Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

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