a poisonous substance produced during the metabolism and growth of certain microorganisms and some higher plant and animal species
"The honeybee colony was wiped out by a toxin that naturally developed in the pollen they had been feeding on."
A toxic or poisonous substance produced by the biological processes of biological organisms.
"The mushroom hunter knew that eating the deadly caps could cause him to ingest a potent toxin produced naturally by the fungus itself."