Synonyms of dull

1 Syllable: daft, slow, low, blear, shush, thick, slack, stock, bland, faint, dims, dumb, blunt, dim, p, neb, dark, fade, fest, dun, blears, paled, fer
2 Syllables: prosaic, grizzling, numbskull, tedious, dimming, doltish, whitens, smoggiest, hazier, blandest, darkest, clammed, lazy, inkhorn, deaden, blunter, numbed, dusky, shallow, dragging, stocker, roily, drearier, duner, washed-out, earthier, frumpier, tepid, murkier, proser, sluggish, unlax, bleary, donnish, blander, corniest, mopish, sing-song, chalky, smoggy, backward, grizzle, hokey, dumdum, stolid, pallid, hazy, dense, adusk, twilit, fainter, deadens, gravest, cast-down, dowdy, dismal, downcast, shushes, shushing, laziest, rayless, dimmer, lagging, dragger, boring, dreary, cheerless, murky, paling, gorked, graver, menial, draggier, humdrum, somber, earthy, draggy, slothful, muffled, faintest, dulling, paler, vacuous, fatuous, purblind, quieten, matest, yawner, mousier, bored, tarnish, frumpy, callus, lumpish, blearing, sallow, inert, muddied, doughier, dingy, doughy, daffy, fairish, dumbing, besot, witless, cloudy, muffling, well-worn, gloomier, cloudiest, dowdier, lazier, bluntest, stretchy, cornier, numbing, dingier, frumpish, tristful, dimmed, clamming, whiten, tritest, mater, muddier, inapt, stupid, caked, gunky, singsong, cloudier, dimmest, corny, darker, palest, torpid, bleared, addled, azoic, blunting, sullen, simple, duskier, drawling, schoolish, depress, bloodless, shushed, faded, triter, muddy, listless, brainless, gloomy, mousy
3 Syllables: bromidic, fatheaded, obtuse, abated, ignorant, mineral, samely, edgeless, retarded, indolent, abate, whitened, decolor, quietened, grim-faced, silencing, tarnishes, ill-lighted, unlighted, tarnished, squirrelly, whitening, retardo, phlegmatic, deadening, mothballed, inadept, lethargic, dysphoric, ponderous, spiritless, deadened, quietening, languishing, stupidest, callused, tarnishing, relieving, unhandy, nubilous, opaque, decolors, depresses, whitebread, besotting, cliché-ridden, idiotic, masklike, unstressed, tasteless, aphotic, mediocre, styleless, stupefy, toneless, colorless, half-baked, jejune, subfuse, nondescript, humorless, abating, subfuscous, unbeauteous, overcast, besotted, dim-witted, numskulled, half-witted, thick-headed, white-bread, insentient, thickheaded, slow-witted, forbearant, unready, calluses, slow-moving, unvaried, prolonged, unsightly, moronic, pedantic
4 Syllables: stereotypic, warmed-over, etherize, drearisome, mitigating, overnice, energyless, imbecilic, uninflected, unsharpened, unreactive, pokerfaced, heavy-hearted, crepuscular, overclouded, melancholic, acherontic, decolored, greenish-yellow, matter-of-fact, boneheaded, lamebrained, ill-adapted, unproficient, unsavory, unenjoyable, uninspiring, tiresome, nontranslucent, nontransparent, stereotyped, overused, soporific, unappealing, unaccented, inactive, mass-produced, repetitious, yesterday's, decoloring, boresome, unlively, etherizing, readymade, expressionless, etherized, imbecile, scatterbrained, unclassified, bespattered, feeble-minded, simple-minded, mitigated, emulsified, insensate, nonanimal, mild-mannered, monotonous, wearisome, unindustrious, everyday, mitigate
5 Syllables: platitudinal, unexcitable, unprogressive, unpleasurable, unstimulating, inanimate, anesthetize, inexpressive, decolorized, repetitive, uncomprehending, institutional, undistinguished, stereotypical, uninteresting, underachieving, unidealistic, unimpassioned, unsentimental, hebetudinous, unentertaining, unperceptive, garden-variety, unexceptional, platitudinous, enervative, anesthetizing, interminable, unreflective, lackadaisical, unimpressive, unanimated, reiterative, unintellectual, decolorize, nonvegetable, unmemorable, unnoteworthy, exanimate, iterative, unenergetic, unclassifiable, unmotivated
6 Syllables: alliterative
7 Syllables: recapitulatory