tarnish
/ˈtɑ:nɪʃ; `tɑrnɪʃ/ v
1 [I, Tn] (cause sth to) lose its brightness by being exposed to air or damp （因暴露於空气或潮气）（使某物）失去光泽
mirrors that have tarnished with age 因年深月久而失去光泽的镜子
The brasswork needs polishing it's badly tarnished. 那黄铜制品该擦了--黑糊糊的.
2 [Tn] stain or blemish (a reputation, etc) 玷污, 损害（名誉等）
The firm's good name was badly tarnished by the scandal. 这件丑事玷污了公司的好名声. tarnish, n [C, U]
loss of brightness; stain or blemish 晦暗; 污点; 瑕疵
remove the tarnish from silver 除去银子上的污点.