Spon*ta"ne*ous (?), a. [L. spontaneus, fr. sponte of free will, voluntarily.]
Proceding from natural feeling, temperament, or disposition, or from a native internal proneness, readiness, or tendency, without constraint; as, a spontaneous gift or proportion.
Proceeding from, or acting by, internal impulse, energy, or natural law, without external force; as, spontaneous motion; spontaneous growth.
Produced without being planted, or without human labor; as, a spontaneous growth of wood.
Spontaneous combustion, combustion produced in a substance by the evolution of heat through the chemical action of its own elements; as, the spontaneous combustion of waste matter saturated with oil. -- Spontaneous generation. Biol. See under Generation.
Syn. -- Voluntary; uncompelled; willing. -- Spontaneous, Voluntary. What is voluntary is the result of a volition, or act of choice; it therefore implies some degree of consideration, and may be the result of mere reason without excited feeling. What is spontaneous springs wholly from feeling, or a sudden impulse which admits of no reflection; as, a spontaneous burst of applause. Hence, the term is also applied to things inanimate when they are produced without the determinate purpose or care of man. "Abstinence which is but voluntary fasting, and . . . exercise which is but voluntary labor." J. Seed.
Spontaneous joys, where nature has its play,
The soul adopts, and owns their firstborn away.
-- Spon*ta"ne*ous*ly, adv. -- Spon*ta"ne*ous*ness, n.
© Webster 1913.