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.
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
Pike followed the main line — called the trunk line — which had hoses branching off in other directions.
From Los Angeles Times • Mar. 11, 2026
Trials have been done using "ropeless creels" which have the main line in a container along with a buoy and these are lowered to the seabed with the creels.
From BBC • Mar. 6, 2025
A message The Associated Press left on the city’s Law Department main line seeking comment Monday wasn’t immediately returned.
From Seattle Times • May 27, 2024
This divide-and-conquer strategy is better than repeatedly allowing counterexamples to intrude into the main line of an argument while browbeating readers into looking away.
From "The Sense of Style" by Steven Pinker
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.
