To dull the luster of; discolor, especially by exposure to air or dirt: Being in the ground for so long tarnished the old coins. To detract from or spoil: a tasteless meal that tarnished an otherwise pleasant evening. To bring disgrace to; sully: a scandal that tarnished his reputation. To lose luster; become discolored: a metal that tarnishes quickly. To become less enjoyable or estimable: Her admiration for the movie's producer quickly tarnished. The condition of being tarnished: no sign of tarnish on the frame. A film or layer of discoloration on a metal surface caused by corrosion or oxidation. The condition of being disgraced or made less estimable: the tarnish on his reputation.