DUMB
dumb, mute, silent
(adjective) unable to speak because of hereditary deafness
dumb
(adjective) lacking the power of human speech; “dumb animals”
speechless, dumb
(adjective) temporarily incapable of speaking; “struck dumb”; “speechless with shock”
dense, dim, dull, dumb, obtuse, slow
(adjective) slow to learn or understand; lacking intellectual acuity; “so dense he never understands anything I say to him”; “never met anyone quite so dim”; “although dull at classical learning, at mathematics he was uncommonly quick”- Thackeray; “dumb officials make some really dumb decisions”; “he was either normally stupid or being deliberately obtuse”; “worked with the slow students”
Source: WordNet® 3.1
Etymology 1
Adjective
dumb (comparative dumber, superlative dumbest)
(dated) Unable to speak; lacking power of speech (kept in "deaf, dumb, and blind").
Synonyms: dumbstruck, mute, speechless, wordless
(dated) Silent; unaccompanied by words.
(informal, pejorative, especially of a person) Extremely stupid.
Synonyms: feeble-minded, idiotic, moronic, stupid, Thesaurus:stupid
(figuratively) Pointless, foolish, lacking intellectual content or value.
Synonyms: banal, brainless, dopey, silly, stupid, ridiculous, vulgar
Lacking brightness or clearness, as a colour.
Etymology 2
Verb
dumb (third-person singular simple present dumbs, present participle dumbing, simple past and past participle dumbed)
(dated) To silence.
(transitive) To make stupid.
(transitive) To represent as stupid.
(transitive) To reduce the intellectual demands of.
Source: Wiktionary
Dumb, a. Etym: [AS. dumb; akin to D. dom stupid, dumb, Sw. dumb,
Goth. dumbs; cf. Gr. Deaf, and cf. Dummy.]
1. Destitute of the power of speech; unable; to utter articulate
sounds; as, the dumb brutes.
To unloose the very tongues even of dumb creatures. Hooker.
2. Not willing to speak; mute; silent; not speaking; not accompanied
by words; as, dumb show.
This spirit, dumb to us, will speak to him. Shak.
To pierce into the dumb past. J. C. Shairp.
3. Lacking brightness or clearness, as a color. [R.]
Her stern was painted of a dumb white or dun color. De Foe.
Deaf and dumb. See Deaf-mute.
– Dumb ague, or Dumb chill, a form of intermittent fever which has
no well-defined "chill." [U.S.] -- Dumb animal, any animal except
man; -- usually restricted to a domestic quadruped; -- so called in
contradistinction to man, who is a "speaking animal." -- Dumb cake, a
cake made in silence by girls on St. Mark's eve, with certain mystic
ceremonies, to discover their future husbands. Halliwell.
– Dumb cane (Bot.), a west Indian plant of the Arum family
(Dieffenbachia seguina), which, when chewed, causes the tongue to
swell, and destroys temporarily the power of speech.
– Dumb crambo. See under crambo.
– Dumb show. (a) Formerly, a part of a dramatic representation,
shown in pantomime. "Inexplicable dumb shows and noise." Shak. (b)
Signs and gestures without words; as, to tell a story in dumb show.
– To strike dumb, to confound; to astonish; to render silent by
astonishment; or, it may be, to deprive of the power of speech.
Syn.
– Silent; speechless; noiseless. See Mute.
Dumb, v. t.
Definition: To put to silence. [Obs.] Shak.
Source: Webster’s Unabridged Dictionary 1913 Edition