Entry 1 sense Webster, 1913 buns · IPA /bʌnz/ 01 n. pl. the buttocks. 1. the buttocks.[Slang] See: buttocks Syn. buttocks, arse, butt, backside, bum, can, fundament, hindquarters, hind end, keister, posterior, prat, rear, rear end, rump, stern, seat, tail, tail end, tooshie, tush, bottom, behind, derriere, fanny, ass.