a principal line or route of a railroad, as contrasted with a branch or secondary one.
a principal highway.
Slang.
a prominent and readily accessible vein of the body that may be used for a narcotic's injection.
the act of mainlining.
a fashionable residential district west of Philadelphia.
any fashionable district where socially prominent people live.
railways
the trunk route between two points, usually fed by branch lines
( as modifier )
a main-line station
a main road
First recorded in 1835–45
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The plans follow a trial of satellite connectivity across operators including LNER, South Western Railway and Great Western Railway, with the technology to be rolled out across nationalised main line services through funding worth £57m.
From BBC • May 26, 2026
A government source said the upgrade would "rocket boost connectivity on every main line train in Britain over the next few years, tackling both slow speeds and irritating not-spots".
From BBC • May 26, 2026
The extensive corroborating evidence is just one way the prosecution is cutting off the defense’s main line of attack.
From Los Angeles Times • May 2, 2024
The service was established by Congress as the main line of defense for children who are exploited online.
From Seattle Times • Apr. 22, 2024
The main line had been cleared and the first train rattled slowly through.
From "A Separate Peace" by John Knowles
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
