What does the word mean? "Towards wholeness?"
It's an expanding of the filter that limits how we see reality.
I think it should be synonymous with a feeling of astonished amazement.

Exploring alternative stats of consciousness can allow us to experience reality in a more authentic way.

expanded perceptions and emotional sensitivity

it is a feeling of astonished amazement at the infinite detail of the universe, and at how far our species has come (knowledge of big history helps with this one).

We don't naturally perceive it because our brains of evolved to see what is useful for us – gather resources, build relationships, build things - not to see what is really there.

Without sensitivity and appreciation, the world is a pretty average place. It doesn’t matter if you're at Santorini, Niagara Falls, in the middle of the Amazon, or on the couch at home. There will always be dirt on the ground, the sun in your eyes, spider webs in the corner, your back will be a little bit stiff, and when lunch is coming along will always be in the back of your mind. Always. You have to learn what to filter.
The perfect holiday destinations on Instagram and travel brochures do not exist. You can go all the way there and if you've taken your shitty attitude with you, you'll only be able to see how average they really are. See Travel expectations vs reality.
The problem with this lies totally and completely in your perspective.
The perspective that we have to develop is that everywhere on this Earth is objectively incredible. The machinery of any single insect leaves our modern technology in the dust. The complexity of the ecosystem of someone's lawn is outstanding. But you have to open your ears and take the time to listen.
The objective reality of a person's existence is a world of unfathomable complexity. A common bee has more detailed and intricate engineering than the most advanced fighter jet, a blade of grass converts sunlight into energy with greater efficiency than the most advanced crystalline silicon solar panels. Every ecosystem houses countless myriad, interdependent relationships of which most lie below our conscious awareness.
The computer screen that you are reading this on represents a web of complex international relationships, from mining its raw materials in outback Australia, its refinement and manufacture in the industrial corridors of China, to a global network of distributers and retailers organising armies of retail staff before finally finding its way onto your desk or hand.
The human mind is undergoing a period of waking up; of becoming aware of unfathomable depths while reconciling our need for commonality.
The two can be but are not always antagonistic.
Everyone sees the unseen in proportion to the clarity of his heart, and that depends upon how much he has polished it. Whoever has polished it more sees more — more unseen forms become manifest to him.
Rumi

It's not mind emptiness. Instead, it's wholly embracing what your senses are telling you rather than what your mind is telling you.

It is a waking up

It is a state of consciousness, where the complexity and vastness of the universe can be more directly perceived and felt.
A number of interesting observations can result, such as the 'oneness' the universe that contains no boundaries, including between itself and you.
It is all a single vast ocean, and all of the things you see are but waves on its surface.

What this is, is a level of perception more closely in line with the objective truth of what the universe is - it is 'above' the usual perception that people have, but it is not by any means godhood (although it does feel that way).

It is like a sky above the sky has been revealed, and it has infinite depth.
It's like a blind person seeing for the first time. They have been walking and living in the exact same world, but now they see the same information in a new, large, engrossing dimension. Their vision stretches further than their hearing ever could.
It is a powerful beam of light that illuminates a cavern of infinite depth, and it reveals as much as you dare to see.
It is a spider's strand, itself invisible yet sparkling from a thousand fine dew drops. It is outstretched and rippling in the gentle rhythm of an indoor breeze. That rhythm is the sound of the universe.
It is like sweeping away sand at your feet and uncovering a floor of gold that in every direction stretches to infinity.
Is like waking up for the first time and discovering that for your entire life you have been asleep.

its like seeing the world for the first time

Let's jump into a hypothetical future. There are communities of people living on space stations throughout the solar system. They've got a good education, they've learnt all about evolution and history, they live interesting futuristic lives. But they've never visited Earth.
Imagine if one of these people won a holiday to one of Earths oldest forests. They go there and walk through towering canopies, and an environment of impossible richness. How do you think they'd feel there? Amazed and overwhelmed? That's what I'm trying to rediscover when I'm in the forest, like I'm seeing it for the first time.
Or a historian seeing a historic battlefield or castle that he's learned about for decades for the first time.
Our familiarity with these things normalises the fantastic.

It's like living your whole life in a walled in community in some future dystopia. It's illegal to venture outside the walls, or to even climb them, and so no one does. Your entire world is enclosed.
One day something happens and you rebel, chased by police. You climb to the top of the wall, when your eyes adjust you see that there is an endless field stretching out as far as the eye can see.
Where before you thought there was only nothing.

Discovering this is like venturing outside for the first time. At the end of the day you have to crawl back to your cave, and sometimes you have to stay there for a while before venturing out again. But the real world is waiting.

Mary in the black and white room.
Seeing the colour is enlightenment.
It must be experienced, you can't just understand the concept of colour.

it is difficult to describe the sensation

We talk about these things, but all that we can share is the words that describe things. It can be a little bit like describing a colour. How would you begin to describe the colour green to a blind man? Go, find it, and we will describe it together.
Just as if I talk all the time I cannot hear what anybody else has to say, if I think all the time I cannot think of anything but my own thoughts. If you stop thinking, you can experience reality as really is.
The present. There is no past and future, and there never will be. There is no time. The present is not some tiny thread on a scale of past to future. The present simply is. It boldly, supremely, powerfully, radiantly, is. THIS is everything that will ever be. And it is all there has ever been.
We are all god. Just as Jesus was.
The man in the sky is an idol.

it is conscious self-awareness of what we really

The difference between man in a state of enlightenment to a normal man as is the difference between a rock to a plant, a plant to an animal, or an animal to a man.

It’s a meditative state

This vision is reality. It's a meditative like state. Normally it dislikes conversation and Social things. Minimalistic music can help, but you've still got to hear the outside.

It’s occasional

"With Pascal, As with all other mystics, ecstasy was only a very occasional state. So far as we know, he had only one experience with its joys. Only once was he touched with the divine fires."
Dawn and the Darkest Hour: A Study of Aldous Huxley

It’s the present moment

The answer to God, life and everything. The sum total of the past is the *present*. The present is the answer to questions of the laws of physics and the origins of the universe. The answer is not '42' but rather 'the present'. But it is the *question* that we are looking for.
The present echoes with the past. I perceive it.

Misc notes

different mind states and consciousness

This is a level of self-awareness above that which we utilise each day.
First, we need to examine the idea of alternative kinds and states of consciousness to the standard 21st century, middle class human version of consciousness that we're used to. Not just of alternatives for humans, but the consciousness of animals, and of other potential kinds of consciousness that we are not aware of or even conceive.
There is an entire ocean of consciousness, of potential conscious mental states out there that we know nothing about. This was a very common understanding in most cultures in history, but disappeared in modern western culture. In modern western culture, the assumption is that mental experiences of the average person is basically all there is, and all there will be, that it is the apex of reality. To the degree that even the most obvious extensions of this, animal consciousness, has been denied… 'No animals have consciousness, they don't have minds'… you only have one tiny island of consciousness which is the mental states of modern people. And this is probably nonsense. Just as it would be ridiculous to say that the only possible configuration of matter is the human body, it is ridiculous to say that the only possible configuration of mind is the mind of middle class Americans in the early 21st century. But this is what we've been saying for quite a long time!
[…] There is a whole spectrum of possible mental states, and it is likely that in the coming decades or centuries we will start exploring this ocean of consciousness like the European discoverers in the 14th and 15th centuries who started to explore the oceans of planet Earth.
Yuval Noah Harari, Reality and the Imagination
We need to examine the idea of alternative states and kinds of consciousness to the standard 21st century, middle class human version of consciousness that we're used to.
Not just of alternatives for humans, but the consciousness of animals, and of other potential kinds of consciousness that we are not aware of or even conceive. There may be an entire ocean of potential conscious mental states that we know nothing about.
This was a very common understanding in most cultures in history, but has disappeared in modern western culture. In modern western culture, the assumption is that the mental experiences of the average person is basically all there is, and all there will be, that it is the apex of reality. Even the most obvious extensions of this, animal consciousness, is often denied.
This is probably nonsense. Just as it would be ridiculous to say that the only possible configuration of matter is the human body, it is ridiculous to say that the only possible configuration of mind is the mind of middle class Americans in the early 21st century.
There is a whole spectrum of possible mental states, and it is likely that in the coming decades or centuries we will start exploring this ocean of consciousness like the European discoverers in the 14th and 15th centuries who started to explore the oceans of planet Earth.[/vc_column_text][image_with_animation image_url="9531" alignment="center" animation="None" hover_animation="none" border_radius="none" box_shadow="none" image_loading="default" max_width="100%" max_width_mobile="default"][vc_column_text]
The 21st century, middle class human version of consciousness may be a small part of the possible range of conscious states.
Take a look at some other organism. I mentioned a rat. You can teach a rat to run complicated mazes, turn right, turn left, turn right. There are a lot of things it can do. You cannot teach a rat to run a prime number maze, which is where you're supposed to right at every prime number. You can teach a human that, they have to figure out prime numbers in their head, but then they can do it. But a rat cannot do it with an infinite amount of training. A rat simply does not have that concept so it's a total mystery for rats.That's kind of analogous to the fact that a human embryo cannot grow wings. It's just beyond its capacity. Now the scientifically and philosophically interesting question is, what things beyond human scope? What things are mysteries to us in the same way that prime number mazes are a mystery to rat?
And I think there is a very interesting record of things in the world. The most simple and striking and dramatic one is interaction of objects. You go back to the mediaeval period, in the neoplastic period, it was assumed that there are 'sympathies' and antipathies' Sympathies brought two objects together, and antipathies pushed them apart. When Galileo and modern science begins, these notions are ridiculed... Galileo introduced a conception that guided modern science. The world is a machine. Everything that happens can be duplicated via skilled artisan – in fact it was created by a skilled artisan. But that was called the mechanical philosophy, where everything works like a machine.
And modern science developed on the principle that unless you can show that something works like a machine you haven't explained it. So Galileo at the end of his life was kind of in despair because he had not shown that the movement of the tides or the heavenly bodies could be accounted for by mechanical principles. Descartes thought that he had shown that you couldn't do it. Leibniz had his own version. But that was modern science until Newton. Newton demonstrated there are no machines. Nothing works by mechanical principles. He concluded that it was an absurdity, that no person with any scientific understanding could possibly accept. And he was right but it's true. Scientists just had to kind of accept the fact that the world is not intelligible to us, that's a major mystery, and science changed totally at that point. It happened slowly, so it kind of became assimilated into common sense, but scientists no longer tried to find a picture of the world that is intelligible to our intuitions. What they tried to do is construct theories that are intelligible, but that totally different topic, much lower goal. And that's what that's pushed Newtonian science - that it's all one huge mystery.
But I think there are plenty of others, like take say freedom of will. There are big debates about freedom of will. It kind of striking that everyone who participates in these debates, including the people who write learned tomes showing there is no freedom of will, believe in freedom of will! Otherwise they wouldn't write the learned tomes. I mean if we are all just thermostats of some complicated kind, then what you do is determined on how people act, so what is the point of the effort? Everyone kind of intuitively believes it, I mean we all believe that I can either pick this up, or fraud across the room or not do anything with it... But I think you can speculate about what the core of the problem is. Take a look at human science. There are two concepts that are pretty well understood. One of them is determinacy. Something determined something else. The other one is randomness. Things happen without anything determining them, and that's about it I think. Those are the basic concepts that we comprehend, and freedom of will just doesn't fit in that set of concepts. Well it could be that this is just another mystery for humans. We don't have the right concept. Some Martians might be looking at us and thinking how stupid we are, why do we keep the determinacy and randomness when there is obviously that thing out there that can't point to because I'm a human.
That and many other things that seem imponderable, might turn out to be like this. And once we recognise that were not angels, we are just biological organisms, and as such we must have limits. That's just a point of logic. You could not have any capacities at all if you didn't have limits, because the capacity determine the limits. And then the question comes well, what's beyond the limits? And we have some plausible examples, and there may be many others. And I think that's a fertile direction to explore once we abandon the kind of belief that we can do anything, which is very common belief, and in the modern sciences it is very common.
Noam Chomsky, The Mysteries of Nature

it helps to have a basis of scientific knowledge

A person must be trained on what we know before they can speculate on what we don't know, or their speculation won't have any grounding or meaning.
Talking about the fundamental nature of the universe, and ideas like Buddha nature, are far too advanced for a person that's not trained in at least some of the sciences to be talking about. As a minimum, they must start with hard science and then progress onto that.

there are many intelligent people who wont get it

There are very many intelligent people who understand the subject matter that you talk about: since they study it. They are lawyers, doctors, and teachers. Except these people will often not quite accept the mystical implications that you're talking about.
Some very intelligent people never achieve this realisation. I think it's not surprising - it's pretty far off.
I think that this comes from the fact that they don’t realise how little they actually know - because throughout their lives they have been the smartest, and their way of seeing the world is reinforced by school, and university, and the bureaucratic testing processes of these professions. They don’t realise that there is a whole world of 'unknowing' out there, since they have so successfully conquered the world of 'knowing', and received such praise from society for it. It can become part of their personality and ego. They tend to reject new claims from outsiders about their subject matter, except from leading academics within their field, thus they prefer to be insular.

If and when they become true masters of their field and discover the precipices on the edges of human knowledge, they will come to appreciate the mystical.
It's also a thing that you feel, disconnected from what you know.

You don’t have to be a monk to pass on your genes

In other words - attain your ideal kind of life.

You don’t have to be a monk to pass your genes on to the next generation. In fact if that’s your goal, becoming a monk, particularly the celibate kind, is one of the worst things you can do.
Maybe this is why seeing a truer reality is not a fitness function.

There are many instances of similar experiences thorughout history

There are also many instances of people, all throughout history, 'waking up' to their everyday environment and to themselves, like the fish blinking its eyes and pausing in the midst of its daily routine and *feeling* the same emotions that David described.
This state has been described as a flash of reality, a momentary vision of the world exactly as it is, unblemished by our biases and concerns.
It's often powerful enough to define a person's life.
It's been the basis of innumerable sects and cults, and perhaps of major religions. It's also been described as madness or a temporary flash of insanity.
Will work for some people but not others:
But unlike prophets and mystics of past eras, and unlike our fish, we are human beings in the early 21st century, which puts us a unique position that no other person or animal has ever been in before. We have the benefit of the collective knowledge of over 200 years of the world's best minds examining and meticulously cataloguing every corner of the Earth around us.

Additional notes - General Holotropic state