Main Line
nickname the wealthy suburbs just to the west of Philadelphia, Pennsylvania, extending from Merion to Bryn Mawr to Paoli. From the Paoli Local commuter train that ran out of the main line of the now-defunct Pennsylvania Railroad, carrying businessmen to work and future lexicographers in blue wool jerseys with five white stripes on each arm to school
US, 1987
main line
noun
1
any large blood vein, especially the median cephalic vein US, 1930s.
2
a major vein used for the injection of narcotics, usually heroin US, 1931.
3
at a horse racing track, the area with the greatest concentration of mutual betting machines US, 1951.
4
the general population of a prison US, 1967