n.
1.a metaphor that has occurred so often that it has become a new meaning of the expression (e.g., `he is a snake' may once have been a metaphor but after years of use it has died and become a new sense of the word `snake')
Idiom of the Day
have the last laugh
to make someone seem foolish for laughing at you first
I had the last laugh when I went home early while everyone else had to work late.