Lacking in brightness: a dim room. Emitting only a small amount of light; faint: a dim light bulb. See Synonyms at dark. Lacking luster; dull or subdued: dim, faded colors. Faintly or unclearly perceived; indistinct: a dim figure in the distance; dim, far-off sounds. Lacking sharpness or clarity; vague: a dim recollection; only a dim idea of how the machine worked. Weak or diminished; feeble: dim eyesight; a dim hope. Negative, unfavorable, or disapproving: a dim future in store; takes a dim view of gambling. Dull or slow-witted:"[She] had always seemed rather dim and vacant"(Mary V. Dearborn). A parking light on a motor vehicle. A low beam. Archaic Dusk.