Top Definition
1- gaining significant muscle mass
2- the act of drinking protein shakes, then hollaring "YEAH BEEF IT UP" , one may also do a series of push ups after drink has been chugged.
3- increasing anything in large amounts
Ouch, I was beefin' it up yesturday and I think I'm sick. YEAH BEEF IT UP!
by snuffalufagus November 21, 2007

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