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
Pat Beall, Sun Sentinel, 12 Aug. 2025
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
Rev. Nathan Empsall, MSNBC Newsweek, 21 Oct. 2025
These were typically mainline Protestant churches, such as Methodist or Presbyterian.
—The Conversation, 7 Oct. 2025
Alessandra Freitas, CNN Money, 12 Oct. 2025
The company is also putting out a comprehensive volume collecting every main line Barb Wire comic, plus bonus material, called The Barb Wire Compendium, in February 2026.
—Raechal Shewfelt, Entertainment Weekly, 20 Sep. 2025
See All Example Sentences for mainline
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Verb
That requires forking over grocery money from whatever is left of the cash Trumplandia is mainlining from kids’ dinner plates to the Billionaire Boys Club.
—Pat Beall, Sun Sentinel, 12 Aug. 2025
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
Adjective
This undermines the religious liberty not only of non-Christian Americans but also of mainline Protestants, non-MAGA Catholics, and Black church traditions.
—Rev. Nathan Empsall, MSNBC Newsweek, 21 Oct. 2025
These were typically mainline Protestant churches, such as Methodist or Presbyterian.
—The Conversation, 7 Oct. 2025
Noun
One main line of investigation is that methanol, cheaper than ethanol, may have been intentionally used by counterfeiters to cut liquor production costs.
—Alessandra Freitas, CNN Money, 12 Oct. 2025
The company is also putting out a comprehensive volume collecting every main line Barb Wire comic, plus bonus material, called The Barb Wire Compendium, in February 2026.
—Raechal Shewfelt, Entertainment Weekly, 20 Sep. 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 30 Oct. 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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