Spontaneous \Spon*ta"ne*ous\, a. [L. spontaneus, fr. sponte of free will, voluntarily.]

1. Proceding from natural feeling, temperament, or disposition, or from a native internal proneness, readiness, or tendency, without constraint; as, a spontaneous gift or proportion.

2. Proceeding from, or acting by, internal impulse, energy, or natural law, without external force; as, spontaneous motion; spontaneous growth.

3. 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.

Usage: 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. --Goldsmith. -- Spon*ta"ne*ous*ly, adv. -- Spon*ta"ne*ous*ness, n.

Source: Webster's Revised Unabridged Dictionary (1913)