[meyn-lahyn, -lahyn] /ˈmeɪnˌlaɪn, -ˈlaɪn/
verb (used without object), mainlined, mainlining. Slang.
to inject a narcotic, especially heroin, directly into a vein.
to use or enjoy something without restriction:
"to mainline on TV movies."
verb (used with object), mainlined, mainlining. Slang.
to inject (a narcotic, especially heroin) directly into a vein.
to use, enjoy, or imbibe (something) without restriction:
"mainlining coffee all day long."
having a principal, established, or widely accepted position; major; mainstream:
"the membership of mainline churches."
1935–40, Americanism; v., adj. use of main line
Example Sentences for mainline
First, look at today's mainline media, a hotbed of forty-year-old thinking.
Amenities on the protected side of a mainline levee, including golf courses and some hotels, will remain open.
Overall, he says, evangelical churches grow in members during recessions while mainline ones decline.
Summary of input variables for mainline freeway segments.
The mainline will be one set of alternates and the side and outer roads would be the other.
As the mainline is hauled it is stored directly back onto the reel.
Uncap the mainline to drain, especially if an emitter is not located at the low point in the system, then re-cap.
Word Origin and History for mainline
1934, from main line in Amer.Eng. slang sense "principal vein into which drugs can be injected" (1933).
Online Etymology Dictionary, © 2010 Douglas Harper
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Slang definitions & phrases for mainline


  1. To inject narcotics into a blood vessel; shoot up : after mainlining heroin the night before (1930s+ Narcotics)
  2. To take or administer stimulants or depressants of various sorts : because the economy was mainlining bigger and bigger fixes of inflation/ LA and the San Joaquin valley mainlined northern California water and couldn't wait for the next fix

Dictionary of American Slang
Copyright © 1986 by HarperCollins Publishers
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