The Collaborative International Dictionary of English v.0.48:

Meddle \Med"dle`\, v. i. [imp. & p. p. Meddled; p. pr. & vb.
   n. Meddling.] [OE. medlen to mix, OF. medler, mesler, F.
   m[^e]ler, LL. misculare, a dim. fr. L. miscere to mix.
   [root]271. See Mix, and cf. Medley, Mellay.]
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   1. To mix; to mingle. [Obs.]
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            More to know
            Did never meddle with my thoughts.    --Shak.
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   2. To interest or engage one's self; to have to do; -- in a
      good sense. [Obs.] --Barrow.
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            Study to be quiet, and to meddle with your own
            business.                             --Tyndale.
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   3. To interest or engage one's self unnecessarily or
      impertinently, to interfere or busy one's self improperly
      with another's affairs; specifically, to handle or distrub
      another's property without permission; -- often followed
      by with or in.
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            Why shouldst thou meddle to thy hurt? --2 Kings xiv.
                                                  10.
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            The civil lawyers . . . have meddled in a matter
            that belongs not to them.             --Locke.
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   To meddle and make, to intrude one's self into another
      person's concerns. [Archaic] --Shak.
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   Syn: To interpose; interfere; intermeddle.
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The Collaborative International Dictionary of English v.0.48:

Meddling \Med"dling\, a.
   Meddlesome. --Macaulay.
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WordNet (r) 3.0 (2006):

meddling
    adj 1: intrusive in a meddling or offensive manner; "an
           interfering old woman"; "bustling about self-importantly
           making an officious nuisance of himself"; "busy about
           other people's business" [syn: interfering,
           meddlesome, meddling, officious, busy,
           busybodied]
    n 1: the act of altering something secretly or improperly [syn:
         meddling, tampering]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "meddling":
   busy, busybody, butting-in, forward, forwardness, impertinence,
   impertinent, inquisitive, inquisitiveness, intermeddling,
   intrusiveness, meddlesome, meddlesomeness, nosy, obtrusiveness,
   officious, officiousness, presumption, presumptuous,
   presumptuousness, prying, pushing, pushy, self-appointed, snoopy