darkening

(noun) changing to a darker color. Synonyms: blackening.

(verb) become dark or darker. Synonyms: darken. Example: "The sky darkened."

(verb) tarnish or stain. Synonyms: darken. Example: "A scandal that darkened the family's good name."

(verb) make dark or darker. Synonyms: darken. Example: "Darken a room."

(adj) becoming dark or darker as from waning light or clouding over. Example: "The darkening sky."