[ meyn-lahyn, -lahyn ]
See synonyms for mainline on
verb (used without object),main·lined, main·lin·ing.Slang.
  1. to inject a narcotic, especially heroin, directly into a vein.

  2. to use or enjoy something without restriction: to mainline on TV movies.

verb (used with object),main·lined, main·lin·ing.Slang.
  1. to inject (a narcotic, especially heroin) directly into a vein.

  2. to use, enjoy, or imbibe (something) without restriction: mainlining coffee all day long.

  1. having a principal, established, or widely accepted position; major; mainstream: the membership of mainline churches.

Origin of mainline

1935–40, Americanism; v., adj. use of main line

Other definitions for main line (2 of 3)

main line

  1. a principal line or route of a railroad, as contrasted with a branch or secondary one.

  2. a principal highway.

  1. Slang.

    • a prominent and readily accessible vein of the body that may be used for a narcotic's injection.

    • the act of mainlining.

Origin of main line

First recorded in 1835–45

Other definitions for Main Line (3 of 3)

Main Line

  1. a fashionable residential district west of Philadelphia.

  2. any fashionable district where socially prominent people live.

Other words from Main Line

  • Main-Line, adjective
  • Main-Liner, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use mainline in a sentence

British Dictionary definitions for main line

main line

  1. railways

    • the trunk route between two points, usually fed by branch lines

    • (as modifier): a main-line station

  2. US a main road

  1. (intr) slang to inject a drug into a vein

  1. having an important position, esp having responsibility for the main areas of activity

Derived forms of main line

  • mainliner, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012