The Collaborative International Dictionary of English v.0.48:

Twang \Twang\, n.
   A tang. See Tang a state. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twang \Twang\, v. i. [imp. & p. p. Twanged; p. pr. & vb. n.
   Twanging.] [Of imitative origin; cf. Tang a sharp sound,
   Tinkle.]
   To sound with a quick, harsh noise; to make the sound of a
   tense string pulled and suddenly let go; as, the bowstring
   twanged.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twang \Twang\, v. t.
   To make to sound, as by pulling a tense string and letting it
   go suddenly.
   [1913 Webster]

         Sounds the tough horn, and twangs the quivering string.
                                                  --Pope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twang \Twang\, n.
   1. A harsh, quick sound, like that made by a stretched string
      when pulled and suddenly let go; as, the twang of a
      bowstring.
      [1913 Webster]

   2. An affected modulation of the voice; a kind of nasal
      sound.
      [1913 Webster]

            He has such a twang in his discourse. --Arbuthnot.
      [1913 Webster]

WordNet (r) 3.0 (2006):

twang
    n 1: a sharp vibrating sound (as of a plucked string)
    2: exaggerated nasality in speech (as in some regional dialects)
       [syn: twang, nasal twang]
    v 1: cause to sound with a twang; "He twanged the guitar string"
    2: sound with a twang; "the bowstring was twanging"
    3: twitch or throb with pain
    4: pluck (strings of an instrument); "He twanged his bow"
    5: pronounce with a nasal twang

Moby Thesaurus II by Grady Ward, 1.0:

130 Moby Thesaurus words for "twang":
   accent, aphonia, artificial voice, bark, bawl, belch, bellow,
   blare, blat, blubber, boom, bray, breathe, broad accent, brogue,
   broken speech, broken tones, broken voice, burr, buzz, cackle, caw,
   chant, childish treble, chirp, chirr, choked voice, clang, clangor,
   clank, clash, coo, cracked voice, craunch, croak, crow, crump,
   crunch, dash, drawl, dysarthria, dyslalia, dyslogia, dysphasia,
   dysphonia, dysphrasia, exclaim, falsetto, flute, gasp, grind,
   groan, growl, grumble, grunt, harshness, hawking voice, hiss,
   hoarseness, idioglossia, idiolalia, impairment of speech,
   intimation, jangle, jar, keen, lilt, lisp, lisping, loss of voice,
   mumble, murmur, mutter, muzzy speech, nasal tone, nasalization,
   pant, pick, pipe, pluck, plunk, quaver, rasp, regional accent,
   roar, rumble, scranch, scrape, scratch, scream, screech, scrunch,
   shade, shake, shriek, sibilate, sibilation, sigh, sing, snap,
   snarl, snore, snort, snuffle, sob, speech defect,
   speech impediment, squall, squawk, squeal, streak, strum,
   suspicion, sweep the strings, thrum, thunder, tinge, touch, trace,
   tremor, trumpet, wail, warble, whiff, whine, whisper, yap, yawp,
   yell, yelp