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 WiFi on hundreds of Britain's main line trains is set to be upgraded under government plans.
From BBC • May 26, 2026
It has only once been shut for longer since it opened in 1886 - that was when electric wires were installed 10 years ago as part of the £2.8bn south Wales main line electrification project.
From BBC • May 22, 2026
Pike followed the main line — called the trunk line — which had hoses branching off in other directions.
From Los Angeles Times • Mar. 11, 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
As we trundled back down the main line, I was thinking about all that I had seen.
From "October Sky" by Homer Hickam
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.
