mainline

1 of 3

verb

main·​line ˈmān-ˌlīn 

mainlined; mainlining; mainlines

transitive verb

slang : to take by or as if by injecting into a principal vein

intransitive verb

slang : to mainline a narcotic drug

mainline

2 of 3

adjective

: being part of an established group

also : being in the mainstream

main line

3 of 3

noun

1

: a principal highway or railroad line

2

slang : a principal vein of the circulatory system

Examples of mainline in a Sentence

Verb

His addiction grew worse when he began mainlining.

Recent Examples on the Web

Verb

Like the rest of the world, I’ve been glued to my couch this past weekend, mainlining season 4 of Bridgerton with a quickness. — Fleurine Tideman, Glamour, 2 Feb. 2026

Ivah’s voice, from word one, like mainlining vulnerability—only, patterned like a poet’s dream. — Literary Hub, 17 June 2025

Adjective

Last fall, United put Starlink on its first mainline jet, a Boeing 737-800. — Rob Pegoraro, PC Magazine, 15 Apr. 2026

According to the exploit’s disclosure page, a patch for Copy Fail was added to the mainline Linux kernel on April 1st. — Stevie Bonifield, The Verge, 1 May 2026

Noun

As far as a solution to our big number two problem, there are two main lines of thinking. — Andrew Paul, Popular Science, 25 Mar. 2026

Higher prices are not Apple’s main line of defence against revenue losses. — Ewan Spence, Forbes.com, 27 June 2026

Word History

First Known Use

Verb

1938, in the meaning defined at transitive sense

Adjective

1941, in the meaning defined above

Noun

1841, in the meaning defined at sense 1

Rhymes for mainline

• affine
• airline
• align
• aline
• assign
• baseline
• beamline
• benign
• bloodline
• bovine
• brucine
• byline

Medical Definition

mainline

1 of 2 verb

main·​line ˈmān-ˈlīn 

mainlined; mainlining

transitive verb

slang : to take by or as if by injecting into a principal vein

intransitive verb

slang : to mainline a narcotic drug (as heroin)

main line

2 of 2 noun

slang

: a principal vein of the circulatory system