/ spɒnˈteɪniəs; NAmE spɑːn-/ adjective
1.
not planned but done because you suddenly want to do it :
a spontaneous offer of help
The audience burst into spontaneous applause.
2.
often doing things without planning to, because you suddenly want to do them
3.
( technical ) happening naturally, without being made to happen :
spontaneous remission of the disease
4.
done naturally, without being forced or practised :
a tape recording of spontaneous speech
a wonderfully spontaneous performance of the piece
► spon·tan·eous·ly adverb :
We spontaneously started to dance.
The bleeding often stops spontaneously.
••
WORD ORIGIN
mid 17th cent.: from late Latin spontaneus (from (sua) sponte of (one's) own accord) + -ous .