antioxidant - definition of antioxidant by The Free Dictionary an·ti·ox·i·dant (ăn′tē-ŏk′sĭ-dənt, ăn′tī-) n. 1. A chemical compound or substance that inhibits oxidation. 2. A substance, such as vitamin E, vitamin C, or beta carotene, thought to protect body cells from the damaging effects of oxidation. antioxidant
