dioxin

Short definition from Wiktionary

Noun

1. 1
   The unsaturated six-membered heterocycle having four carbon atoms, two oxygen atoms, and two double bonds (molecular formula C₄H₄O₂); 1,2-dioxin and 1,4-dioxin.
2. 2
   The parent compound dibenzo-1,4-dioxin or dibenzo-p-dioxin (molecular formula C₁₂H₈O₂), in which two benzene rings are connected through two oxygen atoms; dibenzodioxin, oxanthrene.
3. 3
   Any of a broad range of toxic or carcinogenic halogenated polycyclic compounds that occur as byproducts of herbicides.
4. 4
   Any of a broad range of toxic or carcinogenic halogenated polycyclic compounds that occur as byproducts of herbicides: The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; molecular formula C₁₂H₄Cl₄O₂), a persistent organic pollutant of the environment which is generally produced as a byproduct of organic synthesis or when organic materials are burned.