不速之客-----a gate-crasher

例句：
A: I don't know why the nuisance often comes to our parties without being invited.
我不知道为何该讨厌鬼经常没有受邀而来参 加我们的宴会。
B: He's really a thick-skinned gate-crasher.
他真是个厚脸皮的不速之客。

同义词：
an unbidden guest
turn up like a bad shilling