mainline

1. An airline's main operating unit, as opposed to codeshares or regional subsidiaries.

2. The principal route or line of a railway.

   Hauptbahn, Haupteisenbahnstrecke

3. In longline fishing the central line to which the branch lines with baits are attached.

4. The pipeline carrying wastewater to the public drains or a septic tank.

5. (slang)A principal vein into which a drug can be injected.

6. The main repository for a software project, from which different versions (forks) may be split off.

7. The general population of a prison.

regular

• main linealternative