Synonyms for Trigger (same or very similar meaning)
WordNet sense 1 (lever that activates the firing mechanism of a gun):
gun trigger
WordNet sense 2 (put in motion or move to act):
activate, actuate, spark, trip, set off, spark off, touch off, trigger off
WordNet sense 3 (an act that sets in motion some course of events):
induction, initiation
From the ODE community, based on WordNet
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