ret·ro·ne·cine \ˌre.trōˈnēˌsēn, -_sə̇n sometimes ˌrē.t-\noun (-s) Etymology:retrorsine + senecionine : a crystalline amino dihydroxy bicyclic alcohol C8H13NO2 derived from pyrrole and formed by hydrolysis of various alkaloids (as senecionine or monocrotaline)