75 synonyms for dumb such as blockish, at a loss for words, aphasic, as thick as two short planks, and birdbrained. Dumb is an adjective, and its antonyms are smart and intelligent.
At a loss for words, close-mouthed, inarticulate, mum, saying nothing, silent, speechless, taciturn, tight-lipped, tongue-tied, uncommunicative, untalkative, voiceless, and wordless.
Aphasic, aphonic, dumb, mute, unable to speak, and without the power of speech.
As thick as two short planks, birdbrained, blockish, boneheaded, bovine, brain-dead, brainless, chuckleheaded, cretinous, daft, dead from the neck up, dense, dim, dippy, dof, doltish, dopey, dotish, dozy, dull, dull-witted, dunce-like, dunderheaded, empty-headed, fat-headed, foolish, half-baked, half-witted, idiotic, ignorant, imbecilic, lamebrained, lumpish, mindless, moronic, muttonheaded, not the full shilling, obtuse, pea-brained, simple, simple-minded, slow, slow on the uptake, slow-witted, soft in the head, stupid, thick, thick-skulled, thickheaded, unintelligent, vacuous, vapid, witless, and wooden-headed.