adj
- 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.
- Normal, principal or standard.
- Of a sequence of opening moves: being part of a main line ("a standard sequence of opening moves considered to be best play").
verb
- 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.
noun
- 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.
- The principal route or line of a railway.
- 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.
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