spontaneous

Adjective

spontaneous (comparative more spontaneous, superlative most spontaneous)

1. Self-directed; happening or acting without external cause or instigation; proceeding from natural feeling, temperament, or momentary impulse.
   • He made a spontaneous offer of help.
   • Lady Bertram agreed to it all with a calm “Yes”; and at the end of a quarter of an hour’s silent consideration spontaneously observed, “Sir Thomas, I have been thinking—and I am very glad we took Fanny as we did, for now the others are away we feel the good of it.”1792, Mary Wollstonecraft, A Vindication of the Rights of Woman, J. Johnson

   Synonyms:

   autonomous, automatic, involuntary, natural, unforced

   Antonyms:

   induced, stimulated, voluntary

2. Done by one's own free choice, or without planning.
   • YSL, as he is often called, is equally capable of casual, aristocratic cruelty and earthy, spontaneous tenderness, and when you study his face it can be hard to distinguish boredom from rapture.2015 May 7, A. O. Scott, “Review: ‘Saint Laurent,’ Beautiful People, High Fashion and Career at Its Pinnacle”, in The New York Times, →ISSN, archived from the original on 18 Sep 2019

   Synonyms:

   impulsive, extemporaneous, unpremeditated, unprompted

   Antonyms:

   calculated, deliberate, planned, premeditated

3. Controlled and directed internally; self-active; spontaneous movement characteristic of living things.
4. Produced without being planted or without human cultivation or labor.
   • He 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., […], →OCLC
5. Sudden, without warning.
6. Said or done without prior planning or prior writing.
   • He made spontaneous remarks in the court, after being asked an unexpected question.

   Synonyms:

   unwritten, abrupt, precipitous, subitaneous, precipitant, precipitate, sudden, suddent