The Collaborative International Dictionary of English v.0.48:

Dumb \Dumb\, v. t.
   To put to silence. [Obs.] --Shak.
   [1913 Webster] dumbbell

The Collaborative International Dictionary of English v.0.48:

Dumb \Dumb\, a. [AS. dumb; akin to D. dom stupid, dumb, Sw.
   dumb, Goth. dumbs; cf. Gr. ? blind. See Deaf, and cf.
   Dummy.]
   1. Destitute of the power of speech; unable; to utter
      articulate sounds; as, the dumb brutes.
      [1913 Webster]

            To unloose the very tongues even of dumb creatures.
                                                  --Hooker.
      [1913 Webster]

   2. Not willing to speak; mute; silent; not speaking; not
      accompanied by words; as, dumb show.
      [1913 Webster]

            This spirit, dumb to us, will speak to him. --Shak.
      [1913 Webster]

            To pierce into the dumb past.         -- J. C.
                                                  Shairp.
      [1913 Webster]

   3. Lacking brightness or clearness, as a color. [R.]
      [1913 Webster]

            Her stern was painted of a dumb white or dun color.
                                                  --De Foe.
      [1913 Webster]

   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.
        [1913 Webster]

WordNet (r) 3.0 (2006):

dumb
    adj 1: 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"
           [syn: dense, dim, dull, dumb, obtuse, slow]
    2: temporarily incapable of speaking; "struck dumb"; "speechless
       with shock" [syn: speechless, dumb]
    3: lacking the power of human speech; "dumb animals"
    4: unable to speak because of hereditary deafness [syn: dumb,
       mute, silent]

Moby Thesaurus II by Grady Ward, 1.0:

191 Moby Thesaurus words for "dumb":
   Boeotian, abiotic, anaudic, animal, animalian, animalic,
   animalistic, aphasic, aphonic, apish, asinine, awkward, azoic,
   batty, beastlike, beastly, beef-brained, beef-witted, befooled,
   beguiled, besotted, bestial, blankminded, blockheaded, blockish,
   bovine, brainless, breathless, brief, brusque, brutal, brute,
   brutelike, brutish, buffoonish, callow, chumpish, cloddish, close,
   close-tongued, closemouthed, cockeyed, concise, cowish, crass,
   crazy, credulous, curt, daffy, daft, dazed, dense, dizzy, doltish,
   doting, dull, dullard, dumbfounded, dumbstricken, dumbstruck,
   duncical, duncish, economical of words, empty, empty-headed,
   exanimate, fat, fatheaded, fatuitous, fatuous, flaky, fond, fool,
   foolheaded, foolish, fuddled, futile, gaga, gauche, goofy, green,
   groping, gross, gulled, idiotic, ignorant, imbecile, inane,
   inanimate, inanimated, inarticulate, incoherent,
   indisposed to talk, indistinct, ineducable, inept, inert,
   inexperienced, infatuated, innocent, insane, insensate, insensible,
   insentient, instinctive, instinctual, klutzy, know-nothing, kooky,
   laconic, lifeless, loony, lumpish, mad, maudlin, maundering,
   mindless, moronic, mum, mute, naive, nescient, nonconscious,
   nonliving, nonrational, numskulled, nutty, oafish, opaque, quiet,
   raw, reticent, sappy, screwy, senseless, sentimental, short,
   silent, silly, simple, snug, sottish, soulless, sparing of words,
   speechless, strange to, stricken dumb, stupid, subhuman, taciturn,
   tentative, terse, thick, thick-witted, thoughtless, tight-lipped,
   tongue-tied, tongueless, unacquainted, unanimated, unapprized,
   uncommunicative, uncomprehending, unconscious, unconversant,
   unenlightened, unfamiliar, unfeeling, unilluminated, uninformed,
   uninitiated, unintelligent, unknowing, unloquacious, unposted,
   unripe, unsure, untalkative, unteachable, unversed, vacuous,
   voiceless, wacky, wet, witless, word-bound, wordless, wrongheaded,
   zoic, zooidal, zoologic



Easton's 1897 Bible Dictionary:

Dumb
   from natural infirmity (Ex. 4:11); not knowing what to say
   (Prov. 31:8); unwillingness to speak (Ps. 39:9; Lev. 10:3).
   Christ repeatedly restored the dumb (Matt. 9:32, 33; Luke 11:14;
   Matt. 12:22) to the use of speech.


Bouvier's Law Dictionary, Revised 6th Ed (1856):

DUMB. One who cannot speak; a person who is mute. See Deaf and dumb, Deaf,
dumb, and blind; Mute, standing mute.