Mainline

Etymology

 * main: + line:

Adjective

 * 1) normal, principal or standard.
 * 2)  Of or pertaining to the principal route or line of a railway
 * 3)  Of or pertaining to a surface railway as distinct from an underground, elevated or light rail one.

Synonyms

 * mainstream

Verb

 * 1) To inject (a drug) directly into a vein.

Derived terms

 * mainliner
 * mainlining