main line: Meaning and Definition of

main' line'

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

Main' Line"

1. a fashionable residential district west of Philadelphia.
2. any fashionable district where socially prominent people live.

main•line

1. having a principal, established, or widely accepted position; major; mainstream: the membership of mainline churches.