| adjective | proceeding from natural feeling or impulse without external stimulus “an impulsive gesture of affection” |
| adjective | without forethought “letting him borrow her car was an impulsive act that she immediately regretted” |
| adjective | having the power of driving or impelling “a driving personal ambition” |
| adjective | determined by chance or impulse or whim rather than by necessity or reason “a capricious refusal” |
| adjective | characterized by undue haste and lack of thought or deliberation; ; ; ; ; (`brainish' is archaic) “a hotheaded decision” |
| impulsiveness | noun | the trait of acting suddenly on impulse without reflection |
| impel | verb | urge or force (a person) to an action; constrain or motivate |
| caprice | noun | a sudden desire |
| capriciousness | noun | the trait of acting unpredictably and more from whim or caprice than from reason or judgment |
| whimsy | noun | an odd or fanciful or capricious idea |
| whimsicality | noun | the trait of acting unpredictably and more from whim or caprice than from reason or judgment |
| impetuousness | noun | rash impulsiveness |
| impetuosity | noun | rash impulsiveness |