WordNet (r) 3.0 (2006):

pratfall
    n 1: a fall onto your buttocks
    2: an embarrassing mistake [syn: blunder, blooper,
       bloomer, bungle, pratfall, foul-up, fuckup, flub,
       botch, boner, boo-boo]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "pratfall":
   bloomer, blooper, bobble, bonehead play, boner, boo-boo,
   boob stunt, boot, breakdown, collapse, comedown, crash, cropper,
   culbute, deflation, dive, downfall, dumb trick, fall, flop,
   fool mistake, foozle, forced landing, foul-up, goof, header,
   howler, louse-up, muck-up, nose dive, plunge, screamer, screw-up,
   smash, spill, sprawl, stumble, tailspin, trip, tumble