vi.

1. 变黑；变暗

vt.

1. 使变黑；使变暗
   The commandos blackened their faces with charcoal.

   突击队员用木炭把脸涂黑。

2. 败坏（名誉等）；诋毁
   Don't blacken my name by spreading rumors.

   不要散播流言，破坏我的名誉。

v.

1. become or make black or dark.
2. damage or destroy (someone's reputation).