[1] : WordNet (r) 2.0

keister
     n : 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, posterior, prat, rear,
          rear end, rump, stern, seat, tail, tail end,
          tooshie, tush, bottom, behind, derriere, fanny,
          ass
see also:
buttocks nates arse butt backside bum 
buns can fundament hindquarters hind end 
posterior prat rear rear end rump 
stern seat tail tail end tooshie 
tush bottom behind derriere fanny 
ass 

[2] : Moby Thesaurus II by Grady Ward, 1.0

18 moby thesaurus words for "keister":
   arse, ass, behind, bottom, bum, can, cheeks, duff, fanny,
   posterior, prat, rump, rusty-dusty, stern, tail, tuchis, tush,
   tushy

Keister >> K Words
Keister, definition of term: Keister
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