- to inject a narcotic, especially heroin, directly into a vein.
- to use or enjoy something without restriction: to mainline on TV movies.
- 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.
Origin of mainline
1935–40, Americanism; v., adj. use of main line
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for mainlining
Or was he "mainlining the secret truth of the universe" again?‘True Detective’ Finale Review: Close to Perfection
March 10, 2014
Word Origin and History for mainlining
also main-line, 1934, from main line in American English slang sense "principal vein into which drugs can be injected" (1933).
Online Etymology Dictionary, © 2010 Douglas Harper