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
Lizzy Stroud and her husband Dave run self-catering accommodation in converted train carriages at stations on the Great Western Railway main line at St Germans and Harvey of Hayle, near St Ives in Cornwall.
From BBC ● May 8, 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
Bathtubs and showers cost a bit more, usually starting around $225, and a sewer main line is the most expensive, especially if there are a lot of roots blocking it up.
From Seattle Times ● Jan. 22, 2024
Off to their left, Frank could see the main line of the Fifth Cohort advancing in turtle formation, shields forming a shell over their heads and sides.
From "The Son of Neptune" by Rick Riordan
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
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
In November, a train travelling from Glasgow to London on the West Coast Main Line derailed near Carlisle after hitting a landslip, leaving four people injured.
From BBC ● Dec. 21, 2025
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.
