blacken

Verb

blacken (third-person singular simple present blackens, present participle blackening, simple past and past participle blackened)

1. (causative, transitive) To cause to be or become black.
   • Iron and coal were the magnets that drew railways to this land of lovely valleys and silent mountains—for such it was a century-and-a-half ago, before man blackened the valleys with the smoke of his forges, scarred the green hills with his shafts and waste-heaps, and drove the salmon from the quiet...1939 September, D. S. Barrie, “The Railways of South Wales”, in Railway Magazine, page 157

   Synonyms:

   black, denigrate

2. (ergative, intransitive) To become black.
   • The sky blackened as the storm clouds rolled in.

   Synonyms:

   black up, forswart, swarten

3. (causative, transitive) To make dirty.

   Synonyms:

   dirty, soil, assoil, beclart, bedaub, bedirty, imbrue (especially with blood), bedizen, befile, befilth

4. To defame or sully.

   Synonyms:

   defame, denigrate, sully, taint, tarnish, assassinate, asperse, backbite, badmouth, befoul

5. (transitive) To cook (meat or fish) by coating with pepper, etc., and quickly searing in a hot pan.