Several uninvited guests suddenly showed up at our family gathering.

uninvited 是由前缀 un-（表示"不、非"）和动词 invite（邀请）的过去分词 invited 组合而成，字面意思是"未被邀请的"。 uninvited guests 指"没有被邀请却突然出现的客人"，中文常译为"不速之客"。