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When you are physically incapable of holding in a shit any longer.
I was at Home Depot with my girlfriend when suddenly I reached Critical Mass and had to run to the closest toilet to avoid sitting in my pants. Thank god we were in the plumbing isle.
by Ken "the loose canon" Loveman November 25, 2012
A monthly gathering of people to ride bikes around a city or town. Its general purpose is to raise awareness that people ride bikes for transportation too and roads should be more accomidating for bikes. With many cyclists riding together in a group they are able to reach a "critical mass" and become a powerful entity of the roads, taking up many lanes.

Invented in San Francisco, it is celebrated in many cities across the world due to its simplicity to organize, often all you need to is spread the word about it. In San Francisco and New York participants often number in the thousands. It is usually at the end of the day on the last Friday of every month, at a standard, well-known gathering spot.

Often criticized by motorists as a nuciance, though cyclists criticise back that motorists hog the road, pollute, kill, etc.
Hey bro, want to see a movie this Friday at 5?

No man, I'm going to the Critical Mass to challenge the social norm of owning a car! Me and a few hundred other bike riders are going to be celebrating peaceful transportation. You should come. Everyone should come! No Critical mass? Start one!
by mr. bike March 05, 2006
A large gathering of mostly douchebag hipsters that ride their bikes around the city on the last Friday of the month. Participants feel that since they ride bicycles, they are somehow superior and permitted to break traffic laws.
Did you count the number of hipster douchebags at critical mass? It's over 9000!
by whof arted July 28, 2008
pronounced: /KRIT-ik-ul MAS/

1. (noun) In physics, a measurable point at which a reaction becomes self-sustaining or self-increasing without external force

2. (noun) In sex, the moment when an orgasm is inevitable.

3. (noun) An emotional state of a large group of people which reaches a crescendo (such as in an angry mob or in a concert).

4. (noun) In traffic, the state of having too many cars on the road to effectively move.
1. The atom bomb is intentionally pushed beyond the point of critical mass to create an explosion.

2. When I was fucking my ho, I had to pull out before critical mass so she wouldn't get pregnant.

3. We'd better pull out the riot gear -- this crowd is reaching critical mass.

4. The Interstate has reached critical mass, it's bumper-to-bumper out there!
by Marcus Wright November 08, 2008
Another far left wing terminology to support diversity. Another name for a racial quota.

"Critical mass" means that it is important for a sufficient number of "minorities" to be enrolled on campus so that they not feel "isolated." When the number of blacks dropped at UC Berkeley following the passage of 209, the opponents of 209 argued that the drop in black enrollment created a "hostile environment" for those enrolled. "Critical mass" theory also means that the remainder of the student body needs to see enough black faces so that they can benefit from "diversity."
Don't listen to that hippie fart sniffer, critical mass is just another term for a racial quota.
by Ballsackinthatface April 03, 2013
When something reaches the threshold of it's limits. This can apply to things, people, events, or concepts.
At the party, John told Sue the room had reached critical mass and asked if she wanted to go outside.
by WEW August 29, 2007
the ultimate state of ecstasy or euphoria obtained through ingestion of illicit drug(s) or substance(s)- also known as a "peak." A certain concentration of drug ingested by an individual causes this state of critical mass. Beyond this point of critical mass, further drug intake does not result in increased euphoria or ecstasy.
You want another E? "Nah, I've reached critical mass."
by mattrsf August 19, 2005