WordNet (r) 3.0 (2006):

smash-up
    n 1: a serious collision (especially of motor vehicles) [syn:
         smash, smash-up]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "smashup":
   accident, appulse, blow, breakdown, breaking up, breakup, brunt,
   bulldozing, bulling, bump, calamity, cannon, carambole, carom,
   casualty, cataclysm, catastrophe, cave, cave-in, clash, collapse,
   collision, concussion, contretemps, crack-up, crash, crump, crunch,
   debacle, disaster, encounter, grief, hammering, ill hap, impact,
   impingement, mauling, meeting, misadventure, mischance, misfortune,
   mishap, nasty blow, onslaught, percussion, pileup, ramming,
   shipwreck, shock, sideswipe, sledgehammering, smash, smash-up,
   smashing, staggering blow, thrusting, total loss, tragedy, washout,
   whomp, wrack, wreck