I know that saying. Either the joke exists in several languages or we share one. =)

However, I still generally avoid using that joke with sensitive/more formal matter, preferring to err on the safe side. (Here, as well, misunderstanding might've occurred because the context was a bit less formal than I expected.)

I didn't pay much attention to dictionary references in this thread because I don't trust dictionary much when specific word's usage is in question, more relying on personal experience. Although maybe I should simply get a more extensive dictionary than what ships with OS X—the big problem with the above approach, of course, is that if I never saw a phrase used in some way, it may only mean I never had a chance to.