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
"The Severn Tunnel is the heartbeat of this main line, it's important in connecting communities on each side of the Severn so it's very important that it's operational and reliable."
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
It was the main line from Venice to Trieste, with a high solid embankment, a solid roadbed and double track.
From "A Farewell To Arms" by Ernest Hemingway
Lev, 49, started reaching out to other parents here, in Philadelphia’s wealthy Main Line suburbs, and he found hundreds of families who felt the same way.
From The Wall Street Journal ● Jun. 21, 2026
But East Midlands Railway said engineering work at various points on the Midland Main Line means there will be a reduced timetable and replacement bus services while the festival is on.
From BBC ● May 20, 2026
Cardinale grew up in Villanova, Penn., an affluent suburb on Philadelphia’s Main Line, and attended The Haverford School, an all-boys prep school.
From The Wall Street Journal ● Jan. 16, 2026
The operator said services along the Highland Main Line, between Inverness and Perth, was running.
From BBC ● Jan. 5, 2026
It’s on the prestigious Main Line, just twenty-five minutes outside Philadelphia, on a rolling campus surrounded by overgrown foliage.
From "The Other Wes Moore: One Name, Two Fates" by Wes Moore
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.
