Definitions by Joshiro007
BUCK UP
To challenge someone by getting in their face and disrespecting them with belligerent comments or trying to stare the them down.
I was laughing at this guy behind this one dude and the dude thought I was laughing at him so this nigga had the nerve to BUCK UP to me and I had to lay his ass down.
BUCK UP by Joshiro007 February 12, 2003