Contaminate/kənˈtæmɪneɪt/ Definition 1 of 3Pro Tip 1/3Physical Presence Contamination often requires direct contact with the harmful substance. The sterile bandage was contaminated by dirty hands. Pro Tip 2/3Not Always Visible Impurities from contamination might not be visible to the naked eye. The water looked clean, but was contaminated with bacteria. Pro Tip 3/3Negative Implication 'Contaminate' implies harm or degradation, not just change. The pranksters contaminated the town's fountain with dye.