/her"oh in/ , n. Pharm.
a white, crystalline, narcotic powder, C 21 H 23 NO 5 , 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. Also called diacetylmorphine, diamorphine .
[ 1895-1900; formerly trademark; Heroin hero-, s. of héros HERO + G -in -IN 2 ; allegedly so called from the feelings of power and euphoria which it stimulates ]