A through road.
Of or relating to an artery.
Major, important.
The principal route or line of a railway.
In longline fishing the central line to which the branch lines with baits are attached.
An airline's main operating unit, as opposed to codeshares or regional subsidiaries.
A principal vein into which a drug can be injected.
The main repository for a software project, from which different versions (forks) may be split off.
The pipeline carrying wastewater to the public drains or a septic tank.
Normal, principal or standard.
Of or pertaining to the principal route or line of a railway.
Of or pertaining to a surface railway as distinct from an underground, elevated or light rail one.
Of a sequence of opening moves: being part of a main line ("a standard sequence of opening moves considered to be best play").
To integrate (code, etc.) into the main repository for a software project, rather than separate forks.
To inject (a drug) directly into a vein.
To consume voraciously.