spontaneous

Happening or arising without apparent external cause; self-generated.

Arising from a natural inclination or impulse and not from forethought or prompting.

Unconstrained and unstudied in manner or behavior.

Growing without cultivation or human labor.

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.

Proceeding from natural feeling, temperament, or disposition, or from a native internal proneness, readiness, or tendency, without constraint.