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
Ollie Barder, Forbes.com, 31 July 2025
Late last August, heavy flooding throughout Bangladesh resulted in a similar situation, in which the discharge of cargo from mainline vessels to feeder vessels was suspended.
—Glenn Taylor, Sourcing Journal, 9 July 2025
Freddy Kuo, Forbes.com, 5 Aug. 2025
Therefore, Varda's three main lines of business are military applications, pharmaceutical research and manufacturing, and basic research in microgravity.
—ArsTechnica, 10 July 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
In this instance, what makes the choice of the Nu Gundam notable is that this is a mainline Gundam design penned by the very talented Yutaka Izubuchi and one that was voted the most popular amongst Japanese fans in a 2018 poll hosted by NHK.
—Ollie Barder, Forbes.com, 31 July 2025
Late last August, heavy flooding throughout Bangladesh resulted in a similar situation, in which the discharge of cargo from mainline vessels to feeder vessels was suspended.
—Glenn Taylor, Sourcing Journal, 9 July 2025
Noun
Historically, warehouses have relied on two main lines of defense: live security personnel and video security systems.
—Freddy Kuo, Forbes.com, 5 Aug. 2025
Therefore, Varda's three main lines of business are military applications, pharmaceutical research and manufacturing, and basic research in microgravity.
—ArsTechnica, 10 July 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 19 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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