The Collaborative International Dictionary of English v.0.48:

Addle \Ad"dle\, v. t. & i. [OE. adlen, adilen, to gain, acquire;
   prob. fr. Icel. ["o][eth]lask to acquire property, akin to
   o[eth]al property. Cf. Allodial.]
   1. To earn by labor. [Prov. Eng.] --Forby.
      [1913 Webster]

   2. To thrive or grow; to ripen. [Prov. Eng.]
      [1913 Webster]

            Kill ivy, else tree will addle no more. --Tusser.
      [1913 Webster] Addle-head
      Addle-brain

The Collaborative International Dictionary of English v.0.48:

Addle \Ad"dle\, n. [OE. adel, AS. adela, mud.]
   [1913 Webster]
   1. Liquid filth; mire. [Obs.]
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   2. Lees; dregs. [Prov. Eng.] --Wright.
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The Collaborative International Dictionary of English v.0.48:

Addle \Ad"dle\, a.
   Having lost the power of development, and become rotten, as
   eggs; putrid. Hence: Unfruitful or confused, as brains;
   muddled. --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Addle \Ad"dle\, v. t. & i. [imp. & p. p. Addled; p. pr. & vb.
   n. Addling.]
   To make addle; to grow addle; to muddle; as, he addled his
   brain. "Their eggs were addled." --Cowper.
   [1913 Webster]

WordNet (r) 3.0 (2006):

addle
    v 1: mix up or confuse; "He muddled the issues" [syn: addle,
         muddle, puddle]
    2: become rotten; "addled eggs"

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "addle":
   addle the wits, amaze, astound, baffle, ball up, bamboozle, beat,
   becloud, bedazzle, befuddle, bemuse, besot, bewilder, boggle,
   bother, buffalo, bug, cloud, confound, confuse, daze, dazzle,
   discombobulate, discomfit, discompose, disconcert, disorganize,
   disorient, distract, disturb, dumbfound, embarrass, entangle,
   flabbergast, floor, flummox, flurry, fluster, flutter, fog, fuddle,
   fuss, get, inebriate, intoxicate, keep in suspense, lick, maze,
   mist, mix up, moider, muddle, mystify, nonplus, perplex, perturb,
   pother, put out, puzzle, raise hell, rattle, ruffle, stick, stump,
   throw, throw into confusion, throw off, unsettle, upset