tox·ic / ˈtäksik/ • adj. poisonous: the dumping of toxic waste | alcohol is toxic to the ovaries. ∎  of or relating to poison: toxic hazards. ∎  caused by poison: toxic liver injury.• n. (toxics) poisonous substances.DERIVATIVES: tox·i·cal·ly / -sik(ə)lē/ adv.tox·ic·i·ty / täkˈsisitē/ n.

toxic poisonous XVII; due to poisoning XIX. — medL. toxicus, f. L. toxicum poison — Gr. toxikón (phármakon) (poison) by smearing arrows, n. of toxikós, f. tóxa pl. (bow and) arrows, f. tóxon bow; see -IC.
Hence toxin poison produced by a microbe. XIX.

toxic (toks-ik) adj. having a poisonous effect; potentially lethal.