I'm not sure about that.  Which definition?

I thought money's main necessary properties were

• Mostly conserved.  Sure you might lose some if careless, but you can't duplicate it (double spend, shaving the edge off gold coins, counterfeits).
• Like currency, needs to be transferred around in useful-size easy-to-validate denominations without too much inconvenience (= cost).
• Scarce.  Hence, in part, the Hitchhiker's Guide joke about using leaves off trees as money?  I put it last, but I suspect it is of primary importance.