WordNet (r) 3.0 (2006):

prat
    n 1: the fleshy part of the human body that you sit on; "he
         deserves a good kick in the butt"; "are you going to sit on
         your fanny and do nothing?" [syn: buttocks, nates,
         arse, butt, backside, bum, buns, can,
         fundament, hindquarters, hind end, keister,
         posterior, prat, rear, rear end, rump, stern,
         seat, tail, tail end, tooshie, tush, bottom,
         behind, derriere, fanny, ass]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "prat":
   arse, artifice, ass, backside, behind, bottom, bum, can, gimmick,
   maneuver, play, ploy, rear, ruse, shenanigan, stratagem, tail,
   wile