darkening

Từ điển WordNet v3.1 - WordNet Dictionary

I - noun

changing to a darker color
• Syn:
blackening
• Derivationally related forms:
darken
• Hypernyms:
change of color
• Hyponyms:
obfuscation

II - adjective

becoming dark or darker as from waning light or clouding over (Freq. 1)
- the darkening sky
• Similar to:
dark