Definition of dumb :
1. Destitute of the power of speech; unable; to utter articulate sounds; as, the dumb brutes.
2. Lacking brightness or clearness, as a color.
3. Not willing to speak; mute; silent; not speaking; not accompanied by words; as, dumb show.
4. To put to silence.
lunkheaded, slow-witted, ho-hum, feeble-minded, uncommunicative, boneheaded, empty-headed, bonehead, chuckleheaded, disablement, wordless, closemouthed, dull, wispy, bleak, obtuse, black, gormless, amazed, thudding, lost for words, dimmed, leaden, impenetrable, astounded, dim, tedious, fatuous, mindless, pinheaded, unintelligent, vague, subdued, shocked, weak-minded, tight-lipped, dunderheaded, accessible, hebetudinous, bubbleheaded, irksome, surprised, ataxia, tacit, opaque, unsounded, thick, tiresome, soft, ability, wearisome, thunderstruck, deadening, psyched, faint, softened, unsmart, senseless, developmental disability, dense, aphonic, staggered, reticent, vacuous, the blind, shadowy, simple, understood, purblind, reserved, dimwitted, handicap, close, tongueless, unarticulate, thick-witted, laconic, oafish, dorky, unspoken, witless, silly, knuckleheaded, softheaded, muted, sluggish, heavy, disability, birdbrained, thickheaded, words, disabled, boring, airheaded, astonished, muffled, brain-dead, slow, simple-minded, challenged, lamebrain, inarticulate
dumb (part of speech: adjective)
silent (part of speech: adjective)
foolish (part of speech: adjective)
dim-witted, blithering, blockheaded, absurd, bone-headed, foolish, crazy, inane, crackpot, cretinous, imbecilic, dopey, idiotic, goofy, jackass, brainless, nonsensical, ignorant, nitwit, knuckle-headed, dotty, moronic, half-witted, meat-headed, chuckle-headed, loony, doltish, asinine, stupid, lame-brained
- They questioned me, but I was dumb; and then they kept me prisoner till two days back, when I escaped and came down here." - "One Maid's Mischief", George Manville Fenn.
- She herself had tried to talk art with him, and Peter grew dumb. - "Rose MacLeod", Alice Brown.
- Life alone has any message for life, but from the beginning of time it has put its ear to the cold lips that must for ever remain dumb. - "Annie Kilburn A Novel", W. D. Howells.