adj.自发的，自然的，本能的；自然产生的

He is spontaneous to offer help. 他主动提供帮助。

It is a spontaneous cheer from the crowd. 那是群众自发的喝彩。

The spontaneous applause cut the singer short. 自发的掌声打断了歌唱家的演唱。

The spontaneous combustion of the oil-soaked rags caused the barn to catch fire. 油布碎片的自燃使谷仓起火。