1. (行为)自然的，自发的
Spontaneous acts are not planned or arranged, but are done because someone suddenly wants to do them.
e.g. Diana's house was crowded with happy people whose spontaneous outbursts of song were accompanied by lively music...
戴安娜的家里挤满了兴奋的人们，他们伴着欢快的音乐不由自主地引吭高歌。
e.g. I joined in the spontaneous applause.
我跟着也自然而然地鼓起掌来。