Adjective
1. proceeding from natural feeling or impulse without external stimulus;
"an impulsive gesture of affection"2. without forethought;
"letting him borrow her car was an impulsive act that she immediately regretted"3. having the power of driving or impelling;
"a driving personal ambition""the driving force was his innate enthusiasm""an impulsive force"4. determined by chance or impulse or whim rather than by necessity or reason;
"a capricious refusal""authoritarian rulers are frequently capricious""the victim of whimsical persecutions"5. characterized by undue haste and lack of thought or deliberation;
"a hotheaded decision""liable to such impulsive acts as hugging strangers""an impetuous display of spending and gambling""madcap escapades"; (`brainish' is archaic)