- a white, crystalline, narcotic powder, C21H23NO5, derived from morphine, formerly used as an analgesic and sedative: manufacture and importation of heroin are now controlled by federal law in the U.S. because of the danger of addiction.
- a white odourless bitter-tasting crystalline powder related to morphine: a highly addictive narcotic. Formula: C 21 H 23 NO 5
