mainline

adj

1. (not-comparable)Normal, principal or standard.
2. (US, not-comparable)Not fundamentalist, charismatic or evangelical.

   “At a time when mainline denominations are engaged in massive closures of small rural churches, independent charismatics are strategically helping to rechurch rural Canada.”

   “This doesn’t necessarily mean Christians are joining mainline congregations — the survey measures self-identification, not church affiliation. It is, nevertheless, a striking turnabout after years when mainline Protestantism was considered moribund and evangelical Christianity full of dynamism.”

3. (not-comparable)Of or pertaining to the principal route or line of a railway.
4. (not-comparable)Of or pertaining to a surface-level heavy rail system as distinct from an underground, elevated or light rail one.
5. (not-comparable)Of or pertaining to national or long-distance rail network operators as opposed to urban and suburban operators.

   “Merseyrail and mainline services affected by downpour with more heavy rain forecast”

   “Well-publicised flexible ticketing options are needed for both visitors and workers, integrated across the entire journey: from outside the capital all the way into central London, considering both TfL and mainline rail services.”

6. (not-comparable)Pertaining to a direct route between two major ports.
7. (not-comparable)Of a sequence of opening moves: being part of a main line ("a standard sequence of opening moves considered to be best play").

   “After 3 e5 the Czech Benoni Defense is created. Unlike the mainline 3 e6, which aims for tactical counterplay in the center, Black aims for solidity there. He will choose later what flank to attack on.”

   “Short's pragmatic approach to the match was to avoid mainline theory and the teenager's computer preparation.”

   “The first classical game featured a fairly mainline Nimzo-Indian Defense, with the players following one of So's October 2021 games until move 20.”

verb

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

   “The patient skinpopped for 1½ years and then started to mainline heroin.”

2. (broadly, informal, transitive)To consume voraciously.

   “Last month, she lamented that her busy campaign schedule had kept her from mainlining Amazon’s new “Rings of Power” series.”

3. (transitive)To integrate (code, etc.) into the main repository for a software project, rather than separate forks.
4. (transitive)To include (a prisoner) in the general population of a prison.

noun

1. An airline's main operating unit, as opposed to codeshares or regional subsidiaries.
2. The principal route or line of a railway.
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.

   “Many plumbers will tell you they don't go off property since that is the local water company's responsibility. Most local water companies would prefer that, if a line is snaked, it is snaked all the way to the mainline connection.”

   “In addition, opportunities exist for the introduction of these organisms into a system by means of broken or corroded piping, repair of existing mainlines, installation of new mains, back siphonage, and cross-connections, any of which may result in contamination of the water supply.”

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

   “I'm searching for my mainline / I said I couldn't hit it sideways”

6. The main repository for a software project, from which different versions (forks) may be split off.
7. (alt-of, alternative)Alternative form of main line.

   “8. ...Qe7! is the mainline and Black unpins with Nc6-d8-e6 […]”

8. The general population of a prison.