impulsive

/im-ˈpəl-siv/

adjective

  1. arising from an impulse

  2. prone to act on impulse

  3. acting momentarily

an impulsive decision

an impulsive young man

spontaneous impulsive instinctive automatic mechanical mean acting or activated without deliberation. spontaneous implies lack of prompting and connotes naturalness. impulsive implies acting under stress of emotion or spirit of the moment.