1 obscure, obscured, vague, faint, weak, weakened, pale, imperceptible, fuzzy, indistinct, ill-defined, indiscernible, undefined, indistinguishable, foggy, clouded, cloudy, nebulous, blurred, blurry, unclear, dull, hazy, misty, dark, shadowy, murky, tenebrous, gloomy, sombre, dusky, crepuscular:
Her beauty made The bright world dim. We could barely see in the dim light of the cave.
2 stupid, obtuse, doltish, dull, dull-witted, foolish, slow-witted, dim-witted, dense, Colloq thick, dumb:
Anyone who can't understand that is really quite dim.
3 obscure, dull, becloud:
His natural feelings of compassion had been dimmed by neglect.
4 darken, bedim, shroud, shade:
Twilight dims the sky above. The stage-lights dimmed and the curtain fell.