To go off (In a good way), To get on a roll, Can't be stopped, derived from the term "going ham".
X: Man LeBron James can't be stopped tonight.
Y: Yeah I know, he goin' hammer tonight.

X: I just owned everybody in that round of Call Of Duty deathmatch.
Y: Yeah you were Goin' Hammer
by DThimself December 7, 2010
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