The Collaborative International Dictionary of English v.0.48:

Adulterate \A*dul"ter*ate\, v. t. [imp. & p. p. Adulterated;
   p. pr. & vb. n. Adulterating.] [L. adulteratus, p. p. of
   adulterare, fr. adulter adulterer, prob. fr. ad + alter
   other, properly one who approaches another on account of
   unlawful love. Cf. Advoutry.]
   [1913 Webster]
   1. To defile by adultery. [Obs.] --Milton.
      [1913 Webster]

   2. To corrupt, debase, or make impure by an admixture of a
      foreign or a baser substance; as, to adulterate food,
      drink, drugs, coin, etc.
      [1913 Webster]

            The present war has . . . adulterated our tongue
            with strange words.                   --Spectator.
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   Syn: To corrupt; defile; debase; contaminate; vitiate;
        sophisticate.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Adulterate \A*dul"ter*ate\, v. i.
   To commit adultery. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Adulterate \A*dul"ter*ate\, a.
   1. Tainted with adultery.
      [1913 Webster]

   2. Debased by the admixture of a foreign substance;
      adulterated; spurious.
      [1913 Webster] -- A*dul"ter*ate*ly, adv. --
      A*dul"ter*ate*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

adulterate
    adj 1: mixed with impurities [syn: adulterate, adulterated,
           debased]
    v 1: corrupt, debase, or make impure by adding a foreign or
         inferior substance; often by replacing valuable ingredients
         with inferior ones; "adulterate liquor" [syn: load,
         adulterate, stretch, dilute, debase]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "adulterate":
   alloy, attenuate, baptize, bastardize, canker, cheapen, coarsen,
   confound, contaminate, cook, corrupt, cut, deacon, debase, debauch,
   defile, deflower, degenerate, degrade, denaturalize, denature,
   deprave, desecrate, despoil, devalue, dilute, distort, doctor,
   doctor up, etherealize, expand, fake, falsify, fortify, infect,
   irrigate, juggle, lace, load, manipulate, misuse, pack, pervert,
   plant, poison, pollute, prostitute, rarefy, ravage, ravish, reduce,
   retouch, rig, salt, sophisticate, spike, stack, subtilize, taint,
   tamper with, thin, thin out, twist, ulcerate, violate, vitiate,
   vulgarize, warp, water, water down, weaken, weight