her ‧ o ‧ in /ˈherəʊɪn $ -roʊ-/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: German ; Origin: Greek heros ( ⇨ ↑ hero ); because taking it is said to make people feel heroic ]
a powerful and illegal drug made from ↑ morphine
be on/use/take heroin
a heroin addict