C21 

A room within Kirkland House at Harvard University.
During Session II of Harvard SSP 2008, the room became a legend.
It all started with "Never Have I Ever" and "Truth-or-Dare" but suddenly turned into "Dare-or-Sodemy"
Many things happened, including:
-Mass Orgies
-Gay/Lesbian Sexual Activities
-Scissor Sex
-Guys in Bras
-Sploshing a personal favorite of one of the tenants
-Eating Out
-Fingering
-Handjobs
-Blowjobs
-69
-Hickies
-Threesomes
-Stripteases
-Pole dances
-Lap dances
-Christina bear and Sara bear getting it on

There is also a store that has opened in C21, complete with:
-Masseuses
-Splosher
-Back cracker
-Hickey artist
-Sex Kitten
-Dancer
-Someone that just does EVERYTHING
-Owner of Keith Fucking Moon
-Mommy
-Someone who has retained their dignity

C21 can also be used as a verb...usually applies to anything sexual.

Noun:
a) "Man, we're gonna' have an orgy in C21 tonight!"
b) "I saw one of those C21ers walking down the street, and I remember he was wearing a bra the other night."

Verb:
a) "I totally C21ed last night, it was hot."

C21 by C21ers October 15, 2008

C21 

Twenty first Century

‘as the C21 draws on, water, for example, will join oil as a very precious commodity'

C21 by katkrimar July 30, 2009

C21H26O2 

Chemical formula of Cannabinol, non-phycoactive part which forms into tetrahydrocanabinol (THC)

I dont think that Cheeba had enough C21H26O2 to work... oh wait... hit me like a freight train...

C21H26O2 by Chey kid March 18, 2007

c210k 

Couch to 10k. A method designed to train you from zero fitness to 10K within 12 weeks.

I am in the c210k program preparing for a 10k

c210k by 212person December 8, 2017

C21H26O2 

yo its the chemical formula for tetrahydrocannabinol, the active ingredient in marijuana, yo

yo, yo, u wanna grow some C21 H26 O2?

C21H26O2 by Smokey McPot November 24, 2003