1. characterized by undue haste and lack of thought or deliberation (Freq. 2) - a hotheaded decision - liable to such impulsive acts as hugging strangers - an impetuous display of spending and gambling - madcap escapades ('brainish' is archaic) • Syn: hotheaded, impulsive, madcap, tearaway, brainish • Similar to: incautious • Derivationally related forms: impetuousness, impetuosity, impulsiveness (for: impulsive) • Usage Domain: archaism, archaicism 2. marked by violent force - impetuous heaving waves • Similar to: forceful