bun 1
/bun/ , n.
1. any of a wide variety of variously shaped bread rolls, usually leavened and slightly sweetened or plain, sometimes containing spices, dried currants, etc.
2. hair gathered into a round coil or knot at the nape of the neck or on top of the head in certain coiffures.
3. buns , Slang. the buttocks.
[ 1325-75; ME bunne, of obscure orig. ]
bun 2
/bun/ , n. have a bun on , Slang.
to be intoxicated: Everyone at the party seemed to have a bun on.
[ 1900-05; of uncert. orig. ]