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
Jack King, Vulture, 13 Oct. 2024
The season is long, and cold, and involves a lot of staying in bed on your laptop until 1 pm and also mainlining Oreos while half-watching The Holiday on your mum’s sofa and scrolling Instagram.
—Daisy Jones, Vogue, 22 Oct. 2024
Christopher Cruz, Rolling Stone, 17 Jan. 2025
The 185-year-old American Baptist congregation, located in downtown Waukesha, is slowly reversing what's lately been seen as an inevitable decline among mainline Protestant churches.
—Sophie Carson, Journal Sentinel, 24 Dec. 2024
Christina Shaw, Fox News, 17 Dec. 2024
To avoid line twist and fouling, add a barrel swivel between your main line and leader when fishing a Krocodile.
—Joe Cermele, Outdoor Life, 17 Oct. 2024
See all Example Sentences for mainline 
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Verb
For the guys below the line — not least poor Daniel, who spends his drive to work mainlining his vape while listening to a woefully inadequate meditation tape — there’s existential terror in the air apropos of the arrival of new producer Anita at the end of episode one.
—Jack King, Vulture, 13 Oct. 2024
The season is long, and cold, and involves a lot of staying in bed on your laptop until 1 pm and also mainlining Oreos while half-watching The Holiday on your mum’s sofa and scrolling Instagram.
—Daisy Jones, Vogue, 22 Oct. 2024
Adjective
Like the strategy series they’re derived from, the mainline Dynasty Warriors are based on the 14th-century historical novel Romance of the Three Kingdoms by Luo Guanzhong and are works of fiction set in ancient China.
—Christopher Cruz, Rolling Stone, 17 Jan. 2025
The 185-year-old American Baptist congregation, located in downtown Waukesha, is slowly reversing what's lately been seen as an inevitable decline among mainline Protestant churches.
—Sophie Carson, Journal Sentinel, 24 Dec. 2024
Noun
Call their main line at (805) 383-8703 to participate, the statement said.
—Christina Shaw, Fox News, 17 Dec. 2024
To avoid line twist and fouling, add a barrel swivel between your main line and leader when fishing a Krocodile.
—Joe Cermele, Outdoor Life, 17 Oct. 2024
See all Example Sentences for mainline
Dictionary Entries Near mainline
Cite this Entry
“Mainline.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mainline. Accessed 30 Jan. 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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