Without point or edge
blunt, blunted, dulled, unsharpened, pointless, unpointed, round, square, flat, obtuse, edgeless, turned, nicked, battered, used, broken, toothless, edentate.
Antonyms sharp*, sharpened, keen.
Lacking brightness or color
gloomy, sober, somber, drab, matte, dismal, bleak, dark, dingy, dim, dusky, dun, colorless, plain, obscure, cloudy, lackluster, tarnished, faded, unglazed, lusterless, opaque, leaden, grave, grimy, pitchy, sooty, inky, dead, black, coal-black, unlit, unlighted, sordid, dirty, muddy, murky, gray, ashen, wan, lifeless, rusty, flat, without snap*; see also dark 1.
Antonyms bright*, colorful, gleaming.
Lacking intelligence or sensitivity; said usually of living beings
stupid, stolid, obtuse, sluggish, heavy, slow, retarded, witless, sleepy, backward, dense, dullwitted, tedious, boring, unintelligent, ignorant, unintellectual, vacuous, doltish, besotted, scatterbrained, feeble-minded, half-witted, addled, addlebrained, thick-witted, slow-witted, thick-skulled, imbecilic, insensate, dim, prosy, prosaic, unimaginative, fatuous, insensitive, unfeeling, unresponsive, numb, wooden, blunted, listless, apathetic, phlegmatic, not bright, torpid, spiritless, brainless, shallow, indolent, unentertaining, non compos mentis, simple-minded, simple, moronic, lumpish, stuffy, stodgy, dumb*, thick*, dopey*, lowbrow*, stupid as an ox*, blockheaded*, muscle-bound*, nitwitted*, dimwitted*, dead from the ears up*, not all there*; see also stupid 1.
Antonyms witty*, quick, smart.
Lacking interest; said usually of writing, speaking, or inanimate things
tedious, boring, tiresome, prosy, heavy, leaden, prosaic, trite, hackneyed, monotonous, humdrum, dreary, dismal, dry, arid, barren, colorless, insipid, vapid, flat, bland, uninteresting, deadly, longwinded, prolix, stupid, commonplace, ordinary, common, usual, unenlivened, stuffy, stodgy, old, ancient, stale, moth-eaten, out-of-date, antediluvian, archaic, hoary, worn-out, banal, tired, driveling, senseless, pointless, uninspiring, platitudinous, pedestrian, jejune, tame, routine, familiar, well-known, conventional, unimaginative, depressing, sluggish, plodding, repetitious, unvarying, boresome, abused, repetitive, oft-repeated, well-worn, fatiguing, wearisome, wearing, soporific, producing ennui, lifeless, wooden, characterless, wearying, tiring, unexciting, irksome, stereotyped, stereotypical, stock, the usual thing, the same old thing, slow, draggy, dry as dust, cut and dried, without any kick*, dead as a doornail*, blah*, ho-hum*.
Antonyms exciting*, fascinating, exhilarating.
Not loud or distinct
muffled, muted, low, soft; see faint 3.
Showing little activity
slow, placid, languid, lethargic, still, sluggish, listless, lackadaisical, regular, depressed, inactive, lifeless, spiritless, uneventful, unexciting, slothful, without incident, quiet, even, torpid, inert, bovine, cowlike, routine, usual, accustomed, slack, monotonous, unresponsive, stagnant, dead, boring, falling off, apathetic, stolid, flat, lumpish, lumpy, bearish, poky, off*.
Antonyms stimulating*, lively, active.