The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twiddle \Twid"dle\, v. i.
   To play with anything; hence, to be busy about trifles.
   --Halliwell.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twiddle \Twid"dle\, n.
   1. A slight twist with the fingers.
      [1913 Webster]

   2. A pimple. [Prov. Eng.] --Halliwell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

twiddle
    n 1: a series of small (usually idle) twists or turns
    v 1: turn in a twisting or spinning motion; "The leaves swirled
         in the autumn wind" [syn: twirl, swirl, twiddle,
         whirl]
    2: manipulate, as in a nervous or unconscious manner; "He
       twiddled his thumbs while waiting for the interview" [syn:
       twiddle, fiddle with]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "twiddle":
   babble, cackle, chat, chatter, come in contact, coquet, dabble,
   dally, do nothing, feel, feel of, fiddle, fiddle with,
   fiddle-faddle, fidget, fidget with, finger, finger with, flick,
   flirt, fool, fool around, fool with, fribble, frivol, gab, handle,
   horse around, idle, jerk off, juggle, kid around, loiter,
   manipulate, mess around, mess with, monkey, monkey around,
   monkey with, palm, palpate, paw, piddle, play, play around,
   play with, ply, poke at, potter, prattle, prod, putter, rattle,
   smatter, tap, thumb, tinker, touch, toy, toy with, trifle, twirl,
   waste time, wield, wiggle, yak



The Jargon File (version 4.4.7, 29 Dec 2003):

twiddle
 n.

    1. Tilde (ASCII 1111110, ~). Also called squiggle, sqiggle (sic ?
    pronounced /skig'l/), and twaddle, but twiddle is the most common term.

    2. A small and insignificant change to a program. Usually fixes one bug and
    generates several new ones (see also shotgun debugging).

    3. vt. To change something in a small way. Bits, for example, are often
    twiddled. Twiddling a switch or knobs implies much less sense of purpose
    than toggling or tweaking it; see frobnicate. To speak of twiddling a bit
    connotes aimlessness, and at best doesn't specify what you're doing to the
    bit; ?toggling a bit? has a more specific meaning (see bit twiddling, 
    toggle). 4. Uncommon name for the twirling baton prompt.


The Free On-line Dictionary of Computing (30 December 2018):

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 tweaking 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)