WordNet (r) 3.0 (2006):

slip-up
    n 1: a minor inadvertent mistake usually observed in speech or
         writing or in small accidents or memory lapses etc. [syn:
         slip, slip-up, miscue, parapraxis]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "slipup":
   balk, bevue, blooper, blunder, boner, bungle, error, false move,
   false step, fluff, inadvertence, inadvertency, lapse,
   lapsus calami, lapsus linguae, loose thread, miscue, miss, misstep,
   mistake, near-miss, omission, oversight, slip, stumble, trip,
   wrong step