interloper
noun [ C ] disapproving uk/ˈɪn.təˌləʊ.pər/ us/ˈɪn.t̬ɚˌloʊ.pɚ/
闯入者
someone who becomes involved in an activity or a social group without being asked, or enters a place without permission
Security did not prevent an interloper from getting onto the stage at the opening ceremony. 开幕式上保安没有阻止一名闯入者登上舞台。
Synonym: intruder