main line

noun
1.
a principal line or route of a railroad, as contrasted with a branch or secondary one.
2.
a principal highway.
3.
Slang.
  1. a prominent and readily accessible vein of the body that may be used for a narcotic's injection.
  2. the act of mainlining.
Origin
1835-45

Main Line

noun
1.
a fashionable residential district west of Philadelphia.
2.
any fashionable district where socially prominent people live.
Related forms
Main-Line, adjective
Main-Liner, noun
British Dictionary definitions for main line

main line

noun
1.
(railways)
  1. the trunk route between two points, usually fed by branch lines
  2. (as modifier): a main-line station
2.
(US) a main road
verb
3.
(intransitive) (slang) to inject a drug into a vein
adjective
4.
having an important position, esp having responsibility for the main areas of activity
Derived Forms
mainliner, noun
Word Origin and History for main line
n.

"principal line of a railway," 1841; meaning "affluent area of residence" is by 1917, originally (with capitals) that of Philadelphia, from the "main line" of the Pennsylvania Railroad which added local stops to a string of backwater towns west of the city late 19c. that helped turn them into fashionable suburbs.

The Main Line, Philadelphia's most famous suburban district, was deliberately conceived in the 1870's and 1880's by the [Pennsylvania] Railroad, which built high-toned housing developments, ran hotels, more or less forced its executives to plunk their estates out there, and created a whole series of somewhat spurious Welsh towns along the railroad tracks. ... Now everybody assumes these all date from 1682, like the Robertses; but as Chestnut Hill people like to say, "nobody but Welsh peasants lived on the Main Line till the Railroad built it up." [Nathaniel Burt, "The Perennial Philadelphians," 1963]
The original station stops were, in order out from the city, Overbrook, Merion, Narberth, Wynnewood, Ardmore, Haverford, Bryn Mawr, Paoli. The train line for commuters along it is the Paoli Local.

Slang definitions & phrases for main line

main line

noun phrase
  1. (also Main Line) The wealthy and fashionable elements of a place; high society and its area of residence, esp that of Philadelphia: so young and handsome and so popular with the Main Line (1930s+)
  2. A vein in the arm, the median vein, into which narcotics may be injected (1920s+ Narcotics)

[first sense fr the railroad between Philadelphia and the wealthy suburbs to the west]