Spontaneous means done on the spur of the moment, with no plan behind it. A spontaneous round of applause before the song has finished; the spontaneous decision to get off the train a stop early and walk the rest.
Said of a person it is praise: a spontaneous friend says yes to things and does not need a week's notice. Said of an event it means something started by itself, with no push from outside — spontaneous combustion, a spontaneous recovery, a spontaneous protest that nobody organised. The adverb is spontaneously, and the noun is spontaneity, where the stress jumps and the sound changes to spon-tuh-NAY-uh-tee. Keep it apart from impulsive, which carries a hint that you will regret it. Spontaneous is warm; impulsive is a warning.
1adjectivespontaneousDone suddenly and without planning, out of the feeling of the moment.
“Her spontaneous hug surprised everyone at the table.”
synonyms: unplanned, impromptu, unprompted
2adjectivehappeningHappening by itself, without any outside cause or force.
“Doctors recorded a spontaneous improvement with no change in treatment.”
Also accepted in games: impulsive
Latin
spontāneus
English, today
spontaneous
Learned borrowing from Latin spontāneus.
Etymology from Wiktionary, CC BY-SA