Meaning of Gresham's law

Gresh'am's law'

Pronunciation: [key]
— Econ. Econ.
  1. the tendency of the inferior of two forms of currency to circulate more freely than, or to the exclusion of, the superior, because of the hoarding of the latter.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.