Definition of: tarnish

(tär′nish) v.t.
1. To dim the luster of.
2. To dim the purity of; stain; disgrace.
—v.i.
3. To lose luster, as by oxidation; become blemished. See synonyms under DEFILE¹, STAIN.
—noun
1. Loss of luster; hence, a blemish.
2. The thin film of color on the exposed surface of a metal or mineral. [<OF terniss-, stem of ternir <terne dull, wan]
—tar′nish·a·ble adjective