A rather rude comment one makes to another when they want them to go away. If you are busy, or find the person annoying this is something you might say to them.

It's intent is not to get a laugh, since the meaning of the comment is not very humorous. It is more to make the speaker sound witty.

If somebody says this to you, say no more, just leave the speakers presence. But for goodness sakes, don't take the advice literally!