Thesaurus

anechoic, anserine, apathetic, arid, blockheaded, bloodless, blunt, blunted, boneheaded, boring, bovine, brumous, callous, cloddish, cloud-covered, clouded, cloudlike, cloudy, colorless, colourless, dark, dead, deadened, deadening, dense, desensitised, desensitized, desiccate, desiccated, dim, dispirited, doltish, dopey, dopy, drab, dreary, dull, dulled, dumb, earthbound, edgeless, euphonious, fatheaded, flat, foggy, foolish, gaumless, gentle, gooselike, goosey, goosy, gormless, gray, grey, hard, hazy, heartless, heavy, ho-hum, humdrum, hushed, idle, inactive, indurate, insensible, insensitive, insipid, irksome, jejune, jerky, lackluster, lacklustre, leaden, listless, little, loggerheaded, low, low-toned, lowering, lumpen, lumpish, lusterless, lustreless, mat, matt, matte, matted, miasmal, miasmic, misty, monotonous, muffled, murmuring, murmurous, muted, narcotic, nebular, neutral, nitwitted, nonresonant, numb, obtuse, overcast, pachydermatous, pale, pallid, pedestrian, ponderous, prosaic, prosy, putdownable, quiet, raw, rough, rustling, senseless, slow, sluggish, small, smoggy, soft, soft-footed, soft-spoken, soft-witted, softened, soporiferous, soporific, soughing, soulless, spiritless, strikebound, stupid, subdued, sullen, sunless, susurrant, susurrous, tedious, thick, thick-skinned, thick-skulled, thickheaded, thin, threatening, thudding, tiresome, tough, tough-skinned, unaffected, unanimated, unburnished, unenthusiastic, unexciting, unintelligent, uninteresting, unpolished, unrefined, unresponsive, unreverberant, unsaturated, unsharpened, unstimulating, unthinking, unused, vaporous, vapourous, weak, wearisome, whispering, witless, wooden-headed, yokel-like

dull is a ADJ.

benumb, blunt, damp, dampen, dull, muffle, mute, numb, pall, tone dow, tone down

dull is a VERB.