a white, crystalline powder, an acetyl derivative of morphine, CHNO(CHO): it is a very powerful, habit-forming narcotic whose manufacture and import are prohibited in the U.S.
See heroin in American Heritage Dictionary 4
(hĕrˈō-ĭn)
noun
A white, odorless, bitter crystalline compound, C17H17NO(C2H3O2)2, that is derived from morphine and is a highly addictive narcotic. Also called diacetylmorphine.