Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Happening or arising without apparent external cause; self-generated.
  • adj. Arising from a natural inclination or impulse and not from external incitement or constraint.
  • adj. Unconstrained and unstudied in manner or behavior.
  • adj. Growing without cultivation or human labor.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Self generated; happening without any apparent external cause.
  • adj. Done by one's own free choice, or without planning.
  • adj. proceeding from natural feeling or native tendency without external constraint
  • adj. arising from a momentary impulse
  • adj. controlled and directed internally : self-active : spontaneous movement characteristic of living things
  • adj. produced without being planted or without human labor : indigenous
  • adj. not apparently contrived or manipulated : natural
  • adj. Random.
  • adj. Sudden, without warning.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Proceeding from natural feeling, temperament, or disposition, or from a native internal proneness, readiness, or tendency, without constraint.
  • adj. Proceeding from, or acting by, internal impulse, energy, or natural law, without external force
  • adj. Produced without being planted, or without human labor.

from The Century Dictionary and Cyclopedia

  • Proceeding from a conscious or unconscious internal impulse; occurring or done without the intervention of external causes; in a restricted sense, springing from one's own desire or volition, apart from any external suggestion or incitement.
  • Growing naturally, without previous human care.
  • Growing as native; indigenous.
  • In biology, instinctive or automatic, as some actions of animals which depend upon no external stimulus and are performed without apparent motive or purpose; uninfluenced by external conditions, as a change in structural character. Compare spontaneity, 2.
  • Synonyms Willing, etc. (see voluntary), instinctive, unbidden.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. said or done without having been planned or written in advance
  • adj. happening or arising without apparent external cause

Etymologies

From Late Latin spontāneus, of one's own accord, from Latin sponte.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Late Latin spontaneus, from Latin sponte (sua) ("of one's free will, voluntarily"). (Wiktionary)

Examples

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