What is the meaning of blacken?

verb

• Make or become black.
  • usage: "The smoke blackened the ceiling"; "The ceiling blackened"
  • synonyms: melanize, melanise, nigrify, black
• Burn slightly and superficially so as to affect color.
  • usage: "The cook blackened the chicken breast"; "The fire charred the ceiling above the mantelpiece"; "the flames scorched the ceiling"
  • synonyms: char, sear, scorch