What is enlightenment?

I think the definitions and models (the four path model specifically) from the pragmatic dharma crowd are the most interesting by far. Mostly because they can be tested. It's (Theravada) Buddhism stripped of a lot of the religious dogma.

They describe awakening as an actual, irreversible natural process that can be triggered by concentrating your awareness onto bare experience for a long enough time. Doing this intensively enough will bring about a "discontinuity" / cessation of space-time experience called a "fruition" (nirvana). Coming out of that discontinuity goes with a blissful "what was that?" feeling and some level of understanding of "ultimate reality", meaning a permanent perspective shift (instead of "I am seeing" and "I am hearing": in seeing there is merely the seen, in hearing the heard, etc...).

Shortcut is drugs

My opinion is, it's realizing that your ego is an incredible temporary coincidence and that this doesn't make life meaningless but allows you to choose what meaning you want to give it. Your ego is no more special than the billions of other souls who have rejoined the collective unconsciousness of the universe, which makes us all one in the end.

Realizing that we are all one, man.

But as a continual process - you can't just experience that once and go right back into old habits.. Or you can bring it into everyday interactions with the world. Business, family, politics, science, technology - all the hard stuff.

And it manifests as a cultural phenomenon as well an individual experience.

It when you go beyond the body, mind, and senses and merge into the experience that That alone exists. Analysis will never reach that state.