[spon.ta.ne.ous] adj [LL spontaneus, fr. L sponte of one's free will, voluntarily] (1656) 1: proceeding from natural feeling or native tendency without external constraint
2: arising from a momentary impulse
3: controlled and directed internally: self-acting "~ movement characteristic of living things"
4: produced without being planted or without human labor: indigenous
5: developing without apparent external influence, force, cause, or treatment
6: not apparently contrived or manipulated: natural -- spon.ta.ne.ous.ly adv -- spon.ta.ne.ous.ness n syn spontaneous, impulsive, instinctive, automatic, mechanical mean acting or activated without deliberation. spontaneous implies lack of prompting and connotes naturalness "a spontaneous burst of applause". impulsive implies acting under stress of emotion or spirit of the moment "impulsive acts of violence". instinctive stresses spontaneous action involving neither judgment nor will "blinking is an instinctive reaction". automatic implies action engaging neither the mind nor the emotions and connotes a predictable response "his denial was automatic". mechanical stresses the lifeless, often perfunctory character of the response "a mechanical teaching method".