The Collaborative International Dictionary of English v.0.48:

boner \boner\ n.
   1. an embarrassing mistake.

   Syn: blunder, blooper, bungle, foul-up, flub, botch, boo-boo,
        misdoing.
        [WordNet 1.5]

   2. one who bones food.
      [PJC]

WordNet (r) 3.0 (2006):

boner
    n 1: 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:

49 Moby Thesaurus words for "boner":
   bad job, bevue, bloomer, blooper, blunder, bobble, boggle,
   bonehead play, boo-boo, boob stunt, boot, botch, break, bull,
   bungle, clumsy performance, dumb trick, error, etourderie, faux,
   flub, fluff, fool mistake, foozle, foul-up, fumble, gaffe,
   gaucherie, goof, hash, howler, impropriety, indecorum, lapse,
   louse-up, mess, miscue, mistake, muck-up, muff, off day, pratfall,
   sad work, screamer, screw-up, slip, solecism, stumble, trip