spontaneous

adjective6

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.
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
3. •
   Said or done without prior planning or prior writing.

   • He made spontaneous remarks in the court, after being asked an unexpected question.
4. •
   Controlled and directed internally; self-active; spontaneous movement characteristic of living things.
5. •
   Produced without being planted or without human cultivation or labor.
6. •
   Sudden, without warning.