noun
Slang term for illegal drugs, especially narcotics. Often used in underworld or street contexts.
See also: 麻薬
警察は彼がヤクを売っているところを捕まえた。
The police caught him selling dope.
あの界隈ではヤクの取引がよく行われているらしい。
Apparently drug deals often happen in that area.
Slang reading of 薬, likely derived from the on'yomi やく, used to distinguish illegal drugs from ordinary medicine (くすり).