From the urban Ohio Univeristy dictionary derived from conversations after long nights on Court Street. Coined by a frat boy residing on Stewart St at OU. Beefing on my stacks refers to someone who is dissing on you, hating or showing you disrespect to you, your stacks or your personal possesions. Other terms that could be used are "why you beefing". Someone who always "beefs of your stacks" is considered a "stack beefer".
Craig: "Dude your room is a mess and we are having a party tonight!"
Chris "Dude, why you beefing on my stacks? I will have the pledges clean it!"