- a general name for a family of chlorinated hydrocarbons, C12H4Cl4O2, typically used to refer to one isomer, TCDD, a by-product of pesticide manufacture: a toxic compound that is carcinogenic and teratogenic in certain animals.
- any of a number of mostly poisonous chemical by-products of the manufacture of certain herbicides and bactericides, esp the extremely toxic 2,3,7,8-tetrachlorodibenzo-para-dioxin
