Definition of "spontaneous"

spontaneous

/spɒnˈteɪ.ni.əs/

adjective
comparative more spontaneous, superlative most spontaneous
1. Self-generated; happening without any apparent external cause.
2. Done by one's own free choice, or without planning.
3. Proceeding from natural feeling or native tendency without external or conscious constraint.
4. Arising from a momentary impulse.
5. Controlled and directed internally; self-active; spontaneous movement characteristic of living things.
6. Produced without being planted or without human cultivation or labor.
  Quotations
  H]e persisted in his design; and, because he would not make his wants known, actually subsisted for several days on hips, haws and sloes, and other spontaneous fruits which he gathered in the woods and fields.
  1751, [Tobias] Smollett, chapter 106, in The Adventures of Peregrine Pickle […], volume IV, London: Harrison and Co., […]
7. Random.
8. Sudden, without warning.