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
Mano Sundaresan, Pitchfork, 10 June 2026
Start mainlining Centrum Silver, Boise.
—Michael Deeds, Idaho Statesman, 10 Mar. 2026
Michael Luo, New Yorker, 14 June 2026
Most recently in 2012, the Vatican stated that even if the Latter-day Saint baptismal rite refers to the Trinity, the church’s beliefs about the identities of the three are so different from Catholic and mainline Christian beliefs that the rite cannot be regarded as a Christian baptism.
—ABC News, 10 June 2026
CBS News, 4 June 2026
Look for authenticity to be a main line of attack against Platner.
—Caroline McCaughey, Boston Herald, 4 June 2026
See All Example Sentences for mainline
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Verb
This era of Jane Remover—the music, which mainlines the noisiest impulses of SounDC, the discourse—is brasher and more acidic than ever.
—Mano Sundaresan, Pitchfork, 10 June 2026
Start mainlining Centrum Silver, Boise.
—Michael Deeds, Idaho Statesman, 10 Mar. 2026
Adjective
Sutton points to, among other factors, a gap between the progressive stances adopted by mainline clergy and the more conservative views of the average mainline churchgoer.
—Michael Luo, New Yorker, 14 June 2026
Most recently in 2012, the Vatican stated that even if the Latter-day Saint baptismal rite refers to the Trinity, the church’s beliefs about the identities of the three are so different from Catholic and mainline Christian beliefs that the rite cannot be regarded as a Christian baptism.
—ABC News, 10 June 2026
Noun
However, operations were closed for approximately 10 hours on the railroad, which is a main line that runs from Chicago, Illinois, to the ports of Los Angeles and Long Beach, BNSF officials told CBS LA.
—CBS News, 4 June 2026
Look for authenticity to be a main line of attack against Platner.
—Caroline McCaughey, Boston Herald, 4 June 2026
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 Jun. 2026.
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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