onlooker/ˈɔnlukə(r); `ɑnˌlʊkɚ/ nperson who watches sth happening (without taking part); spectator 旁观者 By the time the ambulance had arrived, a crowd of onlookers had gathered. 救护车赶到时, 围观的人已经很多了.
牛津英汉双解词典