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