1make or become dark or darker: [no object]:the sky was darkening rapidly [with object]:darken the eyebrows with black powder (as adjective darkened)a darkened room
2make or become angry, unhappy, or gloomy: [no object]:his mood darkened [with object]:the abuse darkened the rest of their lives
[no object] (of someone’s eyes or expression) show anger, sorrow, or another strong negative emotion:Guy’s expression darkened
[with object] (of anger, sorrow, etc.) show in (someone’s eyes or expression):misery darkened her gaze
never darken someone's door
keep away from someone’s home permanently:never darken my door again!