mainline

1 of 3

verb

main·​line ˈmān-ˌlīn How to pronounce mainline (audio)
mainlined; mainlining; mainlines

transitive verb

slang : to take by or as if by injecting into a principal vein

intransitive verb

slang : to mainline a narcotic drug

mainline

2 of 3

adjective

: being part of an established group
also : being in the mainstream

main line

3 of 3

noun

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
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
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 To explain, the original and main line for previous Armored Core kits from Kotobukiya was the standard Variable Infinity series of kits. Ollie Barder, Forbes.com, 7 Aug. 2025 See All Example Sentences for mainline

Word History

First Known Use

Verb

1938, in the meaning defined at transitive sense

Adjective

1941, in the meaning defined above

Noun

1841, in the meaning defined at sense 1

Time Traveler
The first known use of mainline was in 1841

Browse Nearby Words

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Cite this Entry

“Mainline.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mainline. Accessed 5 Sep. 2025.

Medical Definition

mainline

1 of 2 verb
main·​line ˈmān-ˈlīn How to pronounce mainline (audio)
mainlined; mainlining

transitive verb

slang : to take by or as if by injecting into a principal vein

intransitive verb

slang : to mainline a narcotic drug (as heroin)

main line

2 of 2 noun
slang
: a principal vein of the circulatory system
Last Updated: - Updated example sentences
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