I guess the short answer is, it depends.
Our economy, even though it has been through the ringer lately, is still fairly stable. We've never had one of those crises when the dollar is so devalued that one has to literally carry wheelbarrows full of money to purchase a loaf of bread. In those cases, I'd call that money ephemeral.
|WWII Italian money|
|Chinese Hell money|
|Teeny-tiny play money (at right is a real penny!)|