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
Dalton Ross, EW.com, 30 July 2025
The distortions are everywhere: People mainlining fascistic AI slop are occupying an alternate reality.
—Charlie Warzel, The Atlantic, 13 June 2025
Christopher Cruz, Rolling Stone, 22 Aug. 2025
Grace Lutheran faces uncertain future Barker's resignation comes as his former church of nine years, Grace Lutheran, is likely on the brink of closure, facing the same headwinds shuttering many other mainline Protestant churches.
—Sophie Carson, jsonline.com, 21 Aug. 2025
Clare Morell, MSNBC Newsweek, 27 May 2025
Historically, warehouses have relied on two main lines of defense: live security personnel and video security systems.
—Freddy Kuo, Forbes.com, 5 Aug. 2025
See All Example Sentences for mainline
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Verb
Instead, all the chatter on that October 2005 morning was focused on the absolute madman chain-smoking and mainlining coffee to a degree never witnessed before.
—Dalton Ross, EW.com, 30 July 2025
The distortions are everywhere: People mainlining fascistic AI slop are occupying an alternate reality.
—Charlie Warzel, The Atlantic, 13 June 2025
Adjective
After directing nine mainline entries in the series, Kojima moved on from Konami to form his own studio, Kojima Productions, and developed the Death Stranding series, leaving the fate of Metal Gear in complete limbo — until now.
—Christopher Cruz, Rolling Stone, 22 Aug. 2025
Grace Lutheran faces uncertain future Barker's resignation comes as his former church of nine years, Grace Lutheran, is likely on the brink of closure, facing the same headwinds shuttering many other mainline Protestant churches.
—Sophie Carson, jsonline.com, 21 Aug. 2025
Noun
The Justices' other main line of questioning focused on what the technological changes over the last 20 years mean for how effective filtering technology is.
—Clare Morell, MSNBC Newsweek, 27 May 2025
Historically, warehouses have relied on two main lines of defense: live security personnel and video security systems.
—Freddy Kuo, Forbes.com, 5 Aug. 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 31 Aug. 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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