The Collaborative International Dictionary of English v.0.48:

contaminated \contaminated\ adj.
   1. containing undesired or infective microorganisms.

   Syn: dirty, infected.
        [WordNet 1.5]

   2. rendered impure by addition of deleterious substances; as,
      had to boil the contaminated water.

   Syn: polluted.
        [WordNet 1.5]

   3. 1 (Computers) damaged by inclusion of incorrect data or
      information not belonging; as, The file was contaminated
      by a buggy editor.

   Syn: corrupted.
        [PJC]

   4. appearing unethical due to a questionable source or
      motives; -- of money or activities; as, The fund was
      contaminated by a large donation from a mobster.

   Syn: tainted.
        [PJC]

The Collaborative International Dictionary of English v.0.48:

Contaminate \Con*tam"i*nate\ (k[o^]n*t[a^]m"[i^]*n[=a]t), v. t.
   [imp. & p. p. Contaminated; p. pr. & vb. n.
   Contaminating.] [L. contaminatus, p. p. of contaminare to
   bring into contact, to contaminate, fr. contamen contagion,
   for contagmen; con- + root of tangere to touch. See
   Contact.]
   To soil, stain, or corrupt by contact; to tarnish; to sully;
   to taint; to pollute; to defile.
   [1913 Webster]

         Shall we now
         Contaminate our figures with base bribes? --Shak.
   [1913 Webster]

         I would neither have simplicity imposed upon, nor
         virtue contaminated.                     --Goldsmith.

   Syn: To pollute; defile; sully; taint; tarnish; soil; stain;
        corrupt.
        [1913 Webster]

WordNet (r) 3.0 (2006):

contaminated
    adj 1: corrupted by contact or association; "contaminated
           evidence" [ant: uncontaminated]
    2: rendered unwholesome by contaminants and pollution; "had to
       boil the contaminated water"; "polluted lakes and streams"
       [syn: contaminated, polluted]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "contaminated":
   abandoned, activated, autoluminescent, bad, bad for, cankered,
   charged, corrupt, corrupted, debased, debauched, decadent,
   degenerate, degraded, depraved, diseased, dissolute, foul,
   gangrened, gangrenous, harmful, hot, impure, infected, injurious,
   insalubrious, insanitary, irradiated, morally polluted, morbid,
   morbific, mortified, noisome, nonkosher, noxious, pathogenic,
   pathological, peccant, perverted, pestiferous, poisoned, polluted,
   profligate, radiferous, radioactivated, radioactive,
   radioluminescent, reprobate, ritually unclean, rotten, septic,
   sphacelated, steeped in iniquity, tainted, tref, ulcerated,
   ulcerous, unbathed, unclean, uncleanly, unhealthful, unhealthy,
   unhygienic, unpure, unsanitary, unscoured, unscrubbed, unswept,
   unwashed, unwholesome, unwiped, vice-corrupted, vitiated, warped