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
from way back
since a long time ago, for a long time
I know my friend from way back. In fact, we went to elementary school together.