Merriam-Webster Collegiate Dictionary - contaminate

 transitive verb  (-nated; -nating)  Etymology: Middle English, from Latin contaminatus, past participle of contaminare; akin to Latin contingere to have contact with — more at contingent  Date: 15th century  1.  a. to soil, stain, corrupt, or infect by contact or association bacteria ~d the wound  b. to make inferior or impure by admixture iron ~d with phosphorus  2. to make unfit for use by the introduction of unwholesome or undesirable elements  • contaminative adjective  • contaminator noun Synonyms:  ~, taint, pollute, defile mean to make impure or unclean. ~ implies intrusion of or contact with dirt or foulness from an outside source water ~d by industrial wastes. taint stresses the loss of purity or cleanliness that follows contamination tainted meat a politician's tainted reputation. pollute sometimes interchangeable with ~, distinctively may imply that the process which begins with contamination is complete and that what was pure or clean has been made foul, poisoned, or filthy the polluted waters of the river. defile implies befouling of what could or should have been kept clean and pure or held sacred and commonly suggests violation or desecration defile a hero's memory with slanderous innuendo.