The Collaborative International Dictionary
diacetyl morphine
heroin \her"o*in\ (h[~e]r"[-o]*[i^]n), n. (Chem.) a morphine derivative, diacetyl morphine, used to relieve severe pain and as a sedative. It is highly addictive, and its use is strictly controlled in the U.S. by federal law. It is a popular strong narcotic drug of abuse, in part because it is more soluble than morphine. It is sometimes included as one of the components of Brompton's mixture, used to control pain in terminallly ill patients.
Syn: diacetyl morphine, H, horse, junk, scag, shit, smack.