contamination

from WordNet (r) 3.0 (2006)

contamination
    n 1: the state of being contaminated [syn: {contamination},
         {taint}]
    2: a substance that contaminates [syn: {contaminant},
       {contamination}]
    3: the act of contaminating or polluting; including (either
       intentionally or accidentally) unwanted substances or factors
       [syn: {contamination}, {pollution}] [ant: {decontamination}]

from The Collaborative International Dictionary of English v.0.48

Contamination \Con*tam`i*na"tion\
   (k[o^]n*t[a^]m`[i^]*n[=a]"sh[u^]n), n. [L. contaminatio.]
   The act or process of contaminating; pollution; defilement;
   taint; also, that which contaminates.
   [1913 Webster]