litharge UK /ˈlɪθɑːd͡ʒ/US /ˈlɪθɑɹd͡ʒ/ noun1 •lead monoxide (PbO) a toxic solid formed from oxidation of lead in air, and used as a pigment.Yes: living among the cohabations^([sic]) of Faust himself, among the litharge and agate and hyacinth and pearls. — 1947 formslitharges