verb (used without object), main·lined, main·lin·ing. Slang. to inject a narcotic, especially heroin, directly into a vein. to use or enjoy something without restriction: to mainline on TV movies.

What does Mainlining in the lingo of drug abuser mean?

(mān′līn″ĭng) A colloquial term for injecting an illicit drug directly into a vein.

What does it mean to mainline something?

transitive verb. slang : to take by or as if by injecting into a principal vein. intransitive verb. slang : to mainline a narcotic drug.