Entry 1 sense Webster, 1913 Toxicity /täk-sĭs'-ət-ē/ · Tox·ic·i·ty · IPA /tɑkˈsɪs.ə.ti/ 01 n. The quality or state of being toxic or poisonous; poisonousness. 1. The quality or state of being toxic or poisonous; poisonousness.