WordNet (r) 3.0 (2006):

touch off
    v 1: put in motion or move to act; "trigger a reaction";
         "actuate the circuits" [syn: trip, actuate, trigger,
         activate, set off, spark off, spark, trigger off,
         touch off]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "touch off":
   backfire, bank, blast, blow out, blow up, burn, burst, bust,
   conflagrate, detonate, discharge, enkindle, explode, fan the flame,
   feed, feed the fire, fire, fulminate, go off, ignite, inflame,
   kindle, let off, light, light the fuse, light up, rekindle,
   relight, relume, set fire to, set off, set on fire, shoot, spark,
   stir the fire, stoke, stoke the fire, strike a light, torch,
   trigger