The Collaborative International Dictionary of English v.0.48:

Diddle \Did"dle\, v. i. [Cf. Daddle.]
   To totter, as a child in walking. [Obs.] --Quarles.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Diddle \Did"dle\, v. t. [Perh. from AS. dyderian to deceive, the
   letter r being changed to l.]
   To cheat or overreach. [Colloq.] --Beaconsfield.
   [1913 Webster]

WordNet (r) 3.0 (2006):

diddle
    v 1: deprive of by deceit; "He swindled me out of my
         inheritance"; "She defrauded the customers who trusted
         her"; "the cashier gypped me when he gave me too little
         change" [syn: victimize, swindle, rook, goldbrick,
         nobble, diddle, bunco, defraud, scam, mulct,
         gyp, gip, hornswoggle, short-change, con]
    2: manipulate manually or in one's mind or imagination; "She
       played nervously with her wedding ring"; "Don't fiddle with
       the screws"; "He played with the idea of running for the
       Senate" [syn: toy, fiddle, diddle, play]

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "diddle":
   ball, bamboozle, be intimate, beat, beguile, beguile of,
   beguile the time, betray, bilk, bluff, bunco, burn, burn daylight,
   cajole, cheat, cheat on, chisel, chouse, chouse out of, circumvent,
   cog, cog the dice, cohabit, come together, commit adultery, con,
   conjure, consume time, copulate, couple, cover, cozen, crib,
   dabble, dally, dawdle, deceive, defraud, delude, dillydally, do,
   do in, do out of, doodle, double-cross, drone, dupe, euchre,
   finagle, flam, fleece, flimflam, fob, footle, forestall, fornicate,
   fribble, frig, fritter away time, fudge, gammon, get around, gouge,
   gull, gyp, have, have sex, have sexual relations, hoax, hocus,
   hocus-pocus, hornswaggle, humbug, juggle, kill time, lag, lallygag,
   lay, laze, let down, lie with, linger, loaf, loiter, loll,
   lollygag, lose time, lounge, make it with, make love, make out,
   mate, mock, mount, mulct, outmaneuver, outreach, outsmart, outwit,
   overreach, pack the deal, pass the time, piddle, pigeon,
   play one false, poke, potter, practice fraud upon,
   put something over, putter, rook, scam, screw, sell gold bricks,
   serve, service, shave, shortchange, sleep with, snow,
   stack the cards, stick, sting, string along, swindle, take,
   take a dive, take in, thimblerig, throw a fight, trick, trifle,
   two-time, victimize, waste time



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

diddle


    1. vt. To work with or modify in a not-particularly-serious manner. ?I
    diddled a copy of ADVENT so it didn't double-space all the time.? ?Let's
    diddle this piece of code and see if the problem goes away.? See tweak
    and twiddle.

    2. n. The action or result of diddling.

    See also tweak, twiddle, frob.


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

diddle

    (US) To work in a casual manner, or the result of such
   work.  (In the UK "to diddle someone" means to cheat them).

   "I diddled a copy of ADVENT so it didn't double-space all the
   time."  "Let's diddle this piece of code and see if the problem
   goes away."

   Similar to twiddle, less purposeful than tweak.

   [Jargon File]

   (2013-08-18)