onlooker
noun [ C ] uk/ˈɒnˌlʊk.ər/ us/ˈɑːnˌlʊk.ɚ/
旁观者，围观者
someone who watches something that is happening in a public place but is not involved in it
A crowd of curious onlookers soon gathered to see what was happening. 很快聚拢了一群好奇的围观者看发生了什么事。
Synonym: looker-on