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
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
David J. Neal, Miami Herald, 15 Sep. 2025
Over the weekend, this strategy finally bore fruit when Russian forces achieved one of the largest breakthroughs of the war, advancing nearly 10 miles, past Ukraine’s main line of defenses in Donetsk oblast.
—Brady Knox, The Washington Examiner, 11 Aug. 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
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
Drivers heading north out of Miami will want to avoid Interstate 95 as the cleanup continues from a multicar crash that had shut down all main line northbound lanes near the Northwest 81st Street entrance.
—David J. Neal, Miami Herald, 15 Sep. 2025
Over the weekend, this strategy finally bore fruit when Russian forces achieved one of the largest breakthroughs of the war, advancing nearly 10 miles, past Ukraine’s main line of defenses in Donetsk oblast.
—Brady Knox, The Washington Examiner, 11 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 18 Sep. 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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