mainlined; mainlining; mainlines
slang
: to take by or as if by injecting into a principal vein
slang
: to mainline a narcotic drug
: being part of an established group
also
: being in the mainstream
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
Inga, San Diego Union-Tribune, 28 Apr. 2025
The first two factors were mainlined into my young soul by the staff at Janus House; by my Masuk English teacher.
—Cyndy Etler, Hartford Courant, 21 Apr. 2025
Richard D. Mahoney, JSTOR Daily, 30 Apr. 2025
As proof of that, Delta, in contrast to airlines affected by supply chain challenges at Boeing, took delivery of more new mainline aircraft in 2024 than any other carrier – 38 planes – because 100% came from Airbus.
—Simon Mainwaring, Forbes.com, 29 Apr. 2025
Ewan Spence, Forbes.com, 11 Apr. 2025
The first Amtrak Airo train will debut in 2026, but eventually, these trains will be rolled out on several of the rail company’s main lines.
—Evie Carrick, Travel + Leisure, 24 Mar. 2025
See All Example Sentences for mainline
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Verb
It ideally should be mainlined, er, consumed in its purest right-out-of the-jar form.
—Inga, San Diego Union-Tribune, 28 Apr. 2025
The first two factors were mainlined into my young soul by the staff at Janus House; by my Masuk English teacher.
—Cyndy Etler, Hartford Courant, 21 Apr. 2025
Adjective
In a country shackled and scarred by race, religion, gender, and class, much of that rationalized and reified by mainline American churches, the Disciples were genial revolutionists offering inclusion, education, and empowerment for those at the margins.
—Richard D. Mahoney, JSTOR Daily, 30 Apr. 2025
As proof of that, Delta, in contrast to airlines affected by supply chain challenges at Boeing, took delivery of more new mainline aircraft in 2024 than any other carrier – 38 planes – because 100% came from Airbus.
—Simon Mainwaring, Forbes.com, 29 Apr. 2025
Noun
In terms of devices, Google looks to be settled on a main line of the Pixel and Pixel Pro smartphones (with Pro and Pro XL models) in Q3, and the mid-range Pixel A Series in Q1.
—Ewan Spence, Forbes.com, 11 Apr. 2025
The first Amtrak Airo train will debut in 2026, but eventually, these trains will be rolled out on several of the rail company’s main lines.
—Evie Carrick, Travel + Leisure, 24 Mar. 2025
See All Example Sentences for mainline
Cite this Entry
“Mainline.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mainline. Accessed 17 May. 2025.
Copy CitationMedical Definition
mainline
1 of 2 verb
main·line
ˈmān-ˈlīn 
mainlined; mainlining
slang
: to take by or as if by injecting into a principal vein
slang
: to mainline a narcotic drug (as heroin)
main line
2 of 2 noun
slang
: a principal vein of the circulatory system
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