我们有句古语，说“有朋自远方来，不亦乐乎？”可是，有朋友到访并不见得任何时候都是让人高兴的。在你有急事要处理或者着急出门的时候，朋友意外到访就有可能是“不亦悲乎”了。

　　social terrorism means when someone you know comes to visit unexpectedly and inconveniently, often staying for a long time, and you can't tell them to leave without being rude。

　　social terrorism(译为“不速之客”或“社交炸弹”)指有熟人在你不太方便的时候突然到访，而且停留很长时间，你又不能很粗鲁地要求人家离开。

　　for example:

　　yesterday, i was just about to go out, and then the doorbell rang. it was sally, and she invited herself in and stayed for an hour! it was social terrorism!

　　昨天，我正要出门的时候，门铃响了。原来是莎莉，她也不客气就进了屋还待了一个小时！简直就是个不速之客！