A mythical creature, typically one you meet out and get along with perfectly, your ideal, yet fail to get a number from. And without a moments notice they are gone.
You: Damn, that girl/guy was everything I am looking for.
Friend: Why didn't you their number?
You: They left before I had a chance, I swear it was a Unicorn!
by topher730 November 10, 2014
The common definition of a unicorn is a mythical creature that looks like a white horse with a spiralled horn on it's head.

The underground definition of a unicorn is a person that enjoys the swinger lifestyle.
Deborah: Woah look at that stud over there! He must have at least 16 women on him!

Dan: They don't call him Charlie the Unicorn for nothing.
by Pony Battles July 10, 2020
The upper class of the equestrian world. Because of their magical powers and sociopathic tendencies, they are typically land owners, government officials, and general rich, pompous douche bags. They often look down on and exploit the other species- most especially the ponies. Because of their arrogant, self centered nature, and frequent impotence on the part of the male, they have a high divorce rate and combined with the likelihood of being hunted down by goblins for their magical horn, consequently low population- much to the relief of the other species.
That unicorn paid the police to evict all the ponies from their land. I hope he's hunted down by goblins.
by BS234 March 20, 2015
A unicorn is an individual that has all of the ideals and qualities that you are looking for in another human. Like the mystical horned creature, you may never see one of these in person, only in dreams.
I met this guy I thought was a unicorn but turns out he is ___ (insert appropriate word).
by Native_Enimga December 7, 2009
A pretty girl or woman that loves comic books, sci-fi and gaming. They're out there, but it's impossible to catch one.
"Look at the unicorn buying the X-Men comics"
by Bubble Shoot October 25, 2011