—adj. 1. not bright; obscure from lack of light or emitted light: a dim room; a dim flashlight. 2. not seen clearly or in detail; indistinct: a dim object in the distance. 3. not clear to the mind; vague: a dim idea. 4. not brilliant; dull in luster: a dim color. 5. not clear or distinct to the senses; faint: a dim sound. 6. not seeing clearly: eyes dim with tears. 7. tending to be unfavorable; not likely to happen, succeed, be favorable, etc.: a dim chance of winning. 8. not understanding clearly.
9. rather stupid; dim-witted.
10. take a dim view of, to regard with disapproval, skepticism, or dismay: Her mother takes a dim view of her choice of friends.
—v.t. 1. to make dim or dimmer.
2. to switch (the headlights of a vehicle) from the high to the low beam.
—v.i. 1. to become or grow dim or dimmer.
2. dim out, (in wartime) to reduce the night illumination of (a city, ship, etc.) to make it less visible from the air or sea, as a protection from enemy aircraft or ships.