a capricious refusal.
a driving personal ambition.
a hotheaded decision.
an impetuous display of spending and gambling.
an impulsive force.
an impulsive gesture of affection.
authoritarian rulers are frequently capricious.
letting him borrow her car was an impulsive act that she immediately regretted.
liable to such impulsive acts as hugging strangers.
madcap escapades.
the driving force was his innate enthusiasm.
the victim of whimsical persecutions.