(economics) the principle that when two kinds of money having the same denominational value are in circulation the intrinsically more valuable money will be hoarded and the money of lower intrinsic value will circulate more freely until the intrinsically more valuable money is driven out of circulation; bad money drives out good; credited to Sir Thomas Gresham WordNet 3.0 & Open English WordNet

In economics, Gresham's law is a monetary principle stating that "bad money drives out good". Wikipedia

Monetary principle on circulating currency; "bad money drives out good" Wikidata

An economic principle stating that, when a government overvalues one type of money and undervalues another, the undervalued money will leave the country or disappear from circulation into hoards, while the overvalued money will flood into circulation; or "bad money drives out good". Wiktionary