1. a strong spontaneous and irrational motivation; - Example: "his first impulse was to denounce them" - Example: "the urge to find out got him into trouble"
WordNet (r) 3.0 (2006):
irrational impulse
n 1: a strong spontaneous and irrational motivation; "his first
impulse was to denounce them"; "the urge to find out got
him into trouble"