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3.
noun: pertaining to assholes who participate in monthly gatherings of Critical Mass bicycle rides through metropolitan areas (i.e. downtown Chicago) whom are known to think they are holier than thou because they ride a bike. Often with convoluted sense of pride and treat it as a lifestyle instead of what it is...just a mode of transportation.
That guys a critical ass always showing up drunk to ride.

Critical ass blocking traffic once again.
by av99999 July 24, 2008
 
1.
adj. The stage in fat accumulation when fabric can no longer contain the enormity of one's buttocks.
Jesus, I can't zip up these jeans anymore - I've reached critical ass!
by ElinorG September 29, 2006
 
2.
The point at which critical mass of the ass is reached, prompting one to immediately find a bathroom and empty contents of said ass; esp. problematic for the work dumper who would rather get paid to defecate but instead has to take care of business before leaving the house.
Graham: I reached critical ass this morning and was 20 mins late to work.

John: Critical what?
by Grahamfw December 07, 2011
 
4.
This is a point where you are partaking in anal sex and it is a definite problem because the motion of thrusts has produced a plunging effect and now shit is about to spill out in an amount that can accumulate a small or lage pile. When it just already is spilling a little that is also critical ass as this is most commonly how it is reached. I am implying that it doesn't have to be a point where the person receiving the thrusts feels it about to come out or the person thrusting feels an approaching barrier that is progressively preventing more room for penetration or it just begins to feel really mooshy. Those are also critical ass. This is the point where the person receiving the phallus has to inch one self over to a safe receptacle with out letting open the flood gates. It can become a spout to where the person is really taking a full-on dump and not just a spill.
Matt:"Oh no... do you smell that? Oh there's too much grease on the penis now."
Kate:"Oh it's fine...pfffrrrohht. Actually... I think we have reached critical ass."
by Eagle747 August 27, 2009