This has the same flavor as a definition I saw once, but can't remember the origin. It might have been von Mises. I don't remember if this is word for word but it's something like:
Money is the nothing you get for the something you give before you can get anything.
I like this one by Thomas Sowell: "Prices are important not because money is considered paramount but because prices are a fast and effective conveyor of information through a vast society in which fragmented knowledge must be coordinated." -