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]