Definitions
1.nounAn airline's main operating unit, as opposed to codeshares or regional subsidiaries.
2.nounThe main repository for a software project, from which different versions (forks) may be split off.
3.verbTo inject (a drug) directly into a vein.
4.verbTo integrate (code, etc.) into the main repository for a software project, rather than separate forks.
5.adjectiveNormal, principal or standard.
6.adjectiveOf or pertaining to the principal route or line of a railway.
7.adjectiveOf or pertaining to a surface railway as distinct from an underground, elevated or light rail one.