spontaneous-adjectiv
Spontaneous acts are not planned or arranged, but are done because someone suddenly wants to do them.
Ex: Diana's house was crowded with happy people whose spontaneous outburst of song were accompanied by lively music.
A spontaneous event happens because of processes within something rather than being caused by things outside it.
Ex: I had another spontaneous miscarriage at around the 16th to 18th week.
