WordWeb Online

1. Put in motion, initiate (a device, reaction, circuit, etc)
   "touch off the circuits";
   - actuate, trigger, activate, set off, spark off, spark, trigger off
    
2. Cause to start, provoke or initiate (usually something negative or violent)
   "touched off riots"; "touch off a huge argument";
   - kick off [informal], spark off, spark, set off, trigger

Derived forms: touching off, touches off, touched off

Type of: initiate, pioneer