Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This

American Heritage Dictionary - Cite This Source - Share This

spon·ta·ne·ous       (spŏn-tā'nē-əs)  Pronunciation Key  adj.   Happening or arising without apparent external cause; self-generated. Arising from a natural inclination or impulse and not from external incitement or constraint. Unconstrained and unstudied in manner or behavior. Growing without cultivation or human labor. [From Late Latin spontāneus, of one's own accord, from Latin sponte; see (s)pen- in Indo-European roots.] spon·ta'ne·ous·ly adv., spon·ta'ne·ous·ness n. Synonyms: These adjectives mean acting, reacting, or happening without apparent forethought or prompting. Spontaneous applies to what arises naturally rather than resulting from external constraint or stimulus: "The highest and best form of efficiency is the spontaneous cooperation of a free people" (Woodrow Wilson). Impulsive refers to the operation of a sudden urge or feeling not governed by reason: Buying a car was an impulsive act that he immediately regretted. Instinctive implies behavior that is a natural consequence of membership in a species. The term also applies to what reflects or comes about as a result of a natural inclination or innate impulse: Helping people in an emergency seems as instinctive as breathing. Involuntary refers to what is not subject to the control of the will: "People drew in their breath with involuntary surprise and suspense" (Harriet Beecher Stowe). Automatic implies an unvarying mechanical response or reaction: She accepted the subpoena with an automatic "thank you."

Online Etymology Dictionary - Cite This Source - Share This
spontaneous 

WordNet - Cite This Source - Share This

spontaneous
adjective
1.	happening or arising without apparent external cause; "spontaneous laughter"; "spontaneous combustion"; "a spontaneous abortion" [ant: induced]
2.	said or done without having been planned or written in advance; "he made a few ad-lib remarks" [syn: ad-lib]

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

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.