Synonyms for Dull:

adj.

blind (adjective)
unperceptive, uncomprehending.
blunt (adjective)
rounded, unpointed, pointless, obtuse, edgeless, unsharpened, blunt.
boring (adjective)
insipid, tedious, dry, mundane, dreary, prosaic, tiresome, well-worn, depressing, monotonous, humdrum, boring, uninteresting, commonplace, Weariful, wearisome.
boring, uninteresting (adjective)
dismal, plain, unimaginative, worn-out, insipid, pointless, uninspiring, commonplace, arid, ordinary, common, abused, soporific, archaic, humdrum, out-of-date, stale, hackneyed, tired, hoary, tiresome, repetitious, Familiar, trite, dreary, stock, prolix, vapid, repetitive, prosy, dry.
colorless (adjective)
colorless, bleached, lusterless, achromatic, hueless, lackluster, neutral, toneless, faded, pale, white.
dark (adjective)
dun, sooty.
darkish (adjective)
dim.
dead (adjective)
anesthetized.
depressed (adjective)
dysphoric, spiritless, heavy-hearted, tristful, melancholic.
dim (adjective)
Weak-minded.
drab, lackluster in effect on senses (adjective)
dark, soft, somber, sober, obscure, leaden, dusky, muddy, opaque, grimy, dingy, blind, faded, dun, softened, cloudy, muted, muffled, matte, ashen, mousy, sooty, murky.
dull (adjective)
besotted, thick-witted, soporific, sluggish, sleepy, dim, bovine, lethargic, slow, dense, blunt, backward, cloddish, boorish, comatose, benumbed, ponderous, loutish, doltish, apathetic, drowsy, stupefied, obtuse.
dumb (adjective)
vacuous.
expressionless (adjective)
lusterless.
flat (adjective)
vapid.
gray (adjective)
drab, neutral-tint, salt-and-pepper, mole-gray, gun metal, mousy, gray, smoky, lead-gray, iron-gray, dreary, dapple-gray, grizzled, gloomy, pearl-gray, dingy, battleship-gray, somber, pearly, ashen, silvery, leaden, taupe.
inactive (adjective)
benumbed.
insensitive (adjective)
depressed, insensible, lifeless, spiritless, placid, usual, apathetic, listless, regular, languid, quiet, lumpy, inactive, monotonous, stagnant, jejune, torpid, colorless, dead, routine, unresponsive, flat, prosaic, still, accustomed, callous, unexciting, even, heavy.
lethargic (adjective)
languid, lackadaisical, indolent, leisurely, languorous, lifeless, drooping, phlegmatic, apathetic, unhurried, dopey, drugged, lumpish, lethargic, lazy, tired, torpid, insensible, slow, slothful, sluggish, benumbed, leaden, listless.
non-resonant (adjective)
muffled, Damped, dead, deadened, flat, silenced, mute, non-resonant.
not sharp (adjective)
blunted, square, unpointed, unsharpened, blunt, round, edgeless, turned.
numb (adjective)
deadened, insensitive, stupefied, desensitized, anesthetized, numb, dazed, narcotized, drugged.
opaque (adjective)
opaque.
repetitious (adjective)
repetitious.
senseless (adjective)
unperceptive, senseless, soporific, dead, narcotic, insentient, trance-like, callous, swooning, aloof, insensible, oblivious, numb, unfeeling, faint, blacked out, insensitive, comatose, unconscious, anesthetized.
slow-witted (adjective)
slow-witted.
stuporous (adjective)
stuporous.
unaware (adjective)
ignorant.
uneventful (adjective)
slothful.
unimaginative (adjective)
prosaic.
unintelligent (adjective)
brainless, imbecilic, indolent, boring, dim, besotted, stolid, low, doltish, dense, backward, shallow, vacuous, simple-minded, tedious, insensate, witless, simple, ignorant, addled, obtuse, sluggish, slow, scatterbrained, dumb, moronic, Feeble-minded, wearisome.
unprofitable (adjective)
barren.

n.

bad, chronic, agonizing, burning, square, chapped, crippling, turned, agonising, broken, angry, achy, round, acute, used, sharp. decide, influence, sordid, lead to, grave, inky, stir, dark, color, grimy, colorful, bright, pitchy, catch, give, grip, plain, dun, skew, dusky, sober, obscure, pack a punch, sooty, dirty, rusty, muddy, wan, opaque, murky, dismal. backward, quick, unexciting, ignorant, witless, simple, scatterbrained, prosy, stodgy, unimaginative, spiritless, non compos mentis, fatuous, witty, slow-witted, stuffy, unintelligent, blockheaded, trivial, brainless, insensate, dimwitted, Feeble-minded, stolid, vacuous, unresponsive, simple-minded, moronic, addled, shallow, wooden, half-witted, imbecilic. trite, bland, stock, out-of-date, Familiar, hoary, jejune, Fatiguing, ancient, well-worn, abused, stereotypical, exciting, common, pedestrian, repetitive, silly, routine, unvarying, deadly, stale, well-known, stereotyped, worn-out, hackneyed, uninspiring, antediluvian, ordinary, old, platitudinous, banal, barren, archaic, vapid, wearying, idiotic, wearing, repetitious, tiring, fascinating, prolix, usual, conventional. billow, cumulus, cirrocumulus, column, cloud, bank, cirrus, cirrostratus, low, cumulonimbus. uneventful, razor-sharp, regular, double-edged, lumpy, lively, razor-edged, barbed, serrated, accustomed, keen, poky, placid, stimulating, even, Two-edged, left-handed, depressed, stagnant, active. bass, low-pitched, resonant, Weak-minded, ability, hollow, deep, plangent. stuporous, nonprofit, unprofitable, awareness, uneconomical, unhealthy, untapped, not-for-profit, uneconomic, loss-making, underfunded. block out, drown, blind, cut out, uncomprehending, quieten, see. anesthetic, bloodless, feelings, weak, attitude. down, off, increase. drear, Weariful, excite. earthbound, aseptic, uninspired, sterile, flavorless, matter of fact. colors. light. dull (noun)
deadening, muffled, lusterless, dreary, muffle, mute, desiccate, nonresonant, grey, slow, boring, heavy, leaden, unsharpened, dim, dumb, lackluster, matt, damp, lustreless, matte, arid, dense, bovine, humdrum, obtuse, wearisome, inactive, thudding, gray, edgeless, tone down, blunted, dampen, mat, monotonous, muted, benumb, thumping, insensitive, ho-hum, blunt, dulled, unreverberant, Irksome, numb, pall, softened, sluggish, cloudy, drab, matted, deadened, tedious, unsaturated, lacklustre, desiccated, soft, uninteresting, flat, tiresome.
grayness (noun)
dreariness, drabness, Silveriness, mousiness, grayness, dapple-grayness, dinginess, pearliness, gloominess, dullness, Smokiness, leadenness, somberness, ashiness, iron-grayness.
in low spirits (noun)
tristful, melancholic, depressed, dispirited, happy, spiritless, low, wistful, dysphoric, unhappy, blue, downcast, heavy-hearted, sad, down, melancholy, downhearted, dejected, desolate.

v.

blunt (verb)
soften, diminish.
bore (verb)
bore, fatigue, annoy, weary, tranquilize, sedate, tire.
boring (verb)
stodgy, repetitious.
depressing (verb)
dismal.
disable (verb)
cripple, hobble, stupefy, vitiate, hamstring, impair, tamper, cramp, benumb, handicap, botch, abrogate, paralyze, anesthetize, hamper, hinder, prostrate, disarm, scotch, enfeeble, screw up, lame, weaken, stun, deaden, sap, incapacitate, undermine, neutralize, invalidate, disable.
numb (verb)
daze, desensitize, narcotize, drug.
quiet (verb)
muffle, silence, still, turn down, quiet.

Other synonyms:

Grey
grey.
low-pitched, trivial, drear, slow-witted, razor-edged, loss-making, plangent, banal, serrated, stuporous, muddy, unexciting, uneconomic, uneconomical, unprofitable, uncomprehending, unresponsive, underfunded, Weariful, resonant, quieten, idiotic, opaque, sharp, aseptic. deadly, barbed, left-handed, matter of fact, half-witted, shallow, anesthetic, Two-edged, earthbound, double-edged, ordinary, uninspired, hollow, pedestrian, stale. flavorless, insensate, barren, Weak-minded, wan, razor-sharp, unhealthy. cloud, drown, bloodless, wooden, weak, murky, sterile. bass. off. blind. barren
unimaginative.
brownish
dun.
commonplace
platitudinous, common.
conservative
stuffy.
dim
turn down.
flavorless
bland.
hackneyed
trite, stereotyped.
in low spirits
melancholy, downcast, unhappy, depressed, dejected, spiritless, blue, dispirited, melancholic, down, tristful, wistful, heavy-hearted, low, sad, desolate, dysphoric, downhearted.
irksome
Irksome.
old fashioned
square.
ordinary
plain.
quieten
quieten.
repetitious
repetitive.
retarded
Feeble-minded.
routine
uneventful.
shadowy
dusky.
stale
prosy.
stupid
simple.
trite
uninspiring, stock.
unintelligent
simple-minded.
whiten
grizzled.
worn out
hackneyed.
Other relevant words:
wooden, tone down, stolid, dun, dampen, mat, slow-witted, damp, unimaginative, heavy, unintelligent, drown.

Usage examples for dull

  1. Oh yes, for it is so dull here. – The Star-Gazers by George Manville Fenn
  2. But don't you find it a little dull – Captivating Mary Carstairs by Henry Sydnor Harrison
  3. Toto, though dull had a certain rough common sense and pointed this out. – The Heart of Rome by Francis Marion Crawford