v. & n.
v. 1 tr. lessen or destroy the lustre of (metal etc.). 2 tr. impair (one's reputation etc.). 3 intr. (of metal etc.) lose lustre.
n. 1 a a loss of lustre. b a film of colour formed on an exposed surface of a mineral or metal. 2 a blemish; a stain. tarnishable adj.
[ F ternir f. terne dark ]