NOUN: Used to describe the size of the woman your friend slept with the night before. The number describes how fat she was because she was able to exist in 3 bars at exactly the same time. You would be able to say something to her at one bar, tell her to hold on a second, leave for the next bar, and finish your sentence there because she was truly that fat. It is possible for a 4 or 5 bar to exist but the term can only be applied to girls that your friend has slept with.
VERB: The act of plowing into an elephant sized female willingly and drunkenly
That chick over there looks like 3 bar to me, I can feel her gravity pulling me closer, try not to sleep with that one.