blacken

1. (transitive, causative) To cause to be or become black.Examples: "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 Rhondda and the murmuring Taff."causativetransitive

2. (intransitive, ergative) To become black.Examples: "The sky blackened as the storm clouds rolled in."Synonyms: black, denigrateergativeintransitive

3. (transitive, causative) To make dirty.Synonyms: dirty, soilcausativetransitive

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