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
Jack King, Vulture, 13 Oct. 2024
The season is long, and cold, and involves a lot of staying in bed on your laptop until 1 pm and also mainlining Oreos while half-watching The Holiday on your mum’s sofa and scrolling Instagram.
—Daisy Jones, Vogue, 22 Oct. 2024
Rahul Majumdar, Newsweek, 6 Feb. 2025
The Rauma Railway offers a scenic journey from Dombås, connecting with mainline trains from Oslo or Trondheim.
Alternatively, drive via the E136 through breathtaking fjord landscapes.
—David Nikel, Forbes, 17 Dec. 2024
Evan Clark, WWD, 13 Feb. 2025
Pumps forcibly move water from main lines and surrounding reservoirs to those tanks.
—Katie Tarasov, CNBC, 30 Jan. 2025
See all Example Sentences for mainline 
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Verb
For the guys below the line — not least poor Daniel, who spends his drive to work mainlining his vape while listening to a woefully inadequate meditation tape — there’s existential terror in the air apropos of the arrival of new producer Anita at the end of episode one.
—Jack King, Vulture, 13 Oct. 2024
The season is long, and cold, and involves a lot of staying in bed on your laptop until 1 pm and also mainlining Oreos while half-watching The Holiday on your mum’s sofa and scrolling Instagram.
—Daisy Jones, Vogue, 22 Oct. 2024
Adjective
Sony maintained a consistent supply of portable spinoffs of its mainline PlayStation franchises, including Metal Gear, GTA, God of War, and even Persona, which led to the PSP's meteoric success.
—Rahul Majumdar, Newsweek, 6 Feb. 2025
The Rauma Railway offers a scenic journey from Dombås, connecting with mainline trains from Oslo or Trondheim.
Alternatively, drive via the E136 through breathtaking fjord landscapes.
—David Nikel, Forbes, 17 Dec. 2024
Noun
The brand’s main line, which marries accessible luxury with a European flair, is priced between $149 to $1,295.
—Evan Clark, WWD, 13 Feb. 2025
Pumps forcibly move water from main lines and surrounding reservoirs to those tanks.
—Katie Tarasov, CNBC, 30 Jan. 2025
See all Example Sentences for mainline
Dictionary Entries Near mainline
Cite this Entry
“Mainline.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mainline. Accessed 19 Feb. 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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