WordNet (r) 3.0 (2006):

bollix up
    v 1: make a mess of, destroy or ruin; "I botched the dinner and
         we had to eat out"; "the pianist screwed up the difficult
         passage in the second movement" [syn: botch, bodge,
         bumble, fumble, botch up, muff, blow, flub,
         screw up, ball up, spoil, muck up, bungle,
         fluff, bollix, bollix up, bollocks, bollocks up,
         bobble, mishandle, louse up, foul up, mess up,
         fuck up]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "bollix up":
   ball up, bollix, bugger, bugger up, confound, confuse, cook,
   foul up, fumble, garble, gum up, hash up, jumble, louse up,
   mess up, mix up, muck up, muddle, pi, play hell with,
   play hob with, queer, riffle, scramble, screw up, shuffle, sink,
   snafu, snarl up, tumble