spontaneous

/spän-ˈtā-nē-əs/

Late Latin spontāneus "voluntary, unconstrained" (from Latin sponte "of one's own accord, by one's own agency," ablative of *spons —of uncertain origin— + -āneus, suffix forming adjectives from temporal adverbs, from -ānus + -eus -eous-ous

adjective

  1. proceeding from natural feeling or native tendency without external constraint

  2. arising from a momentary impulse

  3. controlled and directed internally : self-acting

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.

noun

  1. self-ignition of combustible material through chemical action (such as oxidation) of its constituents —called also spontaneous ignition

noun

  1. a now discredited notion that living organisms spontaneously originate directly from nonliving matter

A difficulty that we have forgotten lay in the widespread belief in spontaneous generation. Aristotle had written that flies, worms, and other small animals originated spontaneously from putrefying matter.