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A male definition. Adding muscle mass or weight by going to the gym frequently and eating a high-protein diet.
Q: Dude, why are you eating so much meat?
A: I'm trying to bulk up.
by Stud April 11, 2005
vomit - British army slang
After eating the concealed pizza, I grabbed the bog and proceeded to bulk up
by Raeburn June 11, 2006