Source : Webster's Revised Unabridged Dictionary (1913)

Twiddle \Twid"dle\, v. t. [Probably of imitative origin. Cf.
   {Tweedle}.]
   To touch lightly, or play with; to tweedle; to twirl; as, to
   twiddle one's thumbs; to twiddle a watch key. [Written also
   twidle.] --Thackeray.

Twiddle \Twid"dle\, v. i.
   To play with anything; hence, to be busy about trifles.
   --Halliwell.

Twiddle \Twid"dle\, n.
   1. A slight twist with the fingers.

   2. A pimple. [Prov. Eng.] --Halliwell.

Source : WordNet®

twiddle
     n : a series of small (usually idle) twists or turns

twiddle
     v 1: turn in a twisting or spinning motion; "The leaves swirled
          in the autumn wind" [syn: {twirl}, {swirl}, {whirl}]
     2: manipulate, as in a nervous or unconscious manner; "He
        twiddled her thumbs while waiting for the interview" [syn:
         {fiddle with}]

Source : Free On-Line Dictionary of Computing

twiddle
     
        1.  The {tilde} character.
     
        2.  (To make) a small or insignificant change.
        E.g. twiddling a program often fixes one bug and generates
        several new ones (see also {shotgun debugging}).  Bits are
        often twiddled.  Twiddling a switch or knob implies much less
        sense of purpose than toggling or {tweak}ing it; see
        {frobnicate}.  {Bit twiddling} connotes aimlessness, and at
        best doesn't specify what you're doing to the bit; to
        "{toggle} a bit" has a more specific meaning.
     
        [{Jargon File}]
     
        (1995-01-31)