'Toxin' definitions:

Definition of 'toxin'

From: WordNet
noun
A poisonous substance produced during the metabolism and growth of certain microorganisms and some higher plant and animal species

Definition of 'Toxin'

From: GCIDE
  • Toxin \Tox"in\, Toxine \Tox"ine\, n. [Gr. toxiko`n. See Toxic. ] A poisonous product formed by an organism, such as a pathogenic bacterium, a plant or an animal, usually having a high molecular weight, often a protein or a polysaccharide, but occasionally a low-molecular weight agent such as tetrodotoxin.

Synonyms of 'toxin'

From: Moby Thesaurus