main line

¹ American  

noun

1. a principal line or route of a railroad, as contrasted with a branch or secondary one.

2. a principal highway.

3. Slang.

   1. a prominent and readily accessible vein of the body that may be used for a narcotic's injection.

   2. the act of mainlining.

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Main Line ² American  

noun

1. a fashionable residential district west of Philadelphia.

2. any fashionable district where socially prominent people live.

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main line British  

noun

1. railways

   1. the trunk route between two points, usually fed by branch lines

   2. ( as modifier )

      a main-line station

2. a main road

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verb

1. slang (intr) to inject a drug into a vein

adjective

1. having an important position, esp having responsibility for the main areas of activity

Other Word Forms

• Main-Line adjective
• Main-Liner noun
• mainliner noun

Etymology

Origin of main line

First recorded in 1835–45

Example Sentences

Warwickshire Police said its main line of inquiry was that a vehicle had hit the man and left the scene.

From BBC • Apr. 5, 2026

Pike followed the main line — called the trunk line — which had hoses branching off in other directions.

From Los Angeles Times • Mar. 11, 2026

The service was established by Congress as the main line of defense for children who are exploited online.

From Seattle Times • Apr. 22, 2024

It said de-icing fluid would be applied to keep critical junctions open and "proactive changes" on the Highland main line had already protected remote junctions from signal failure.

From BBC • Jan. 15, 2024

Off to their left, Frank could see the main line of the Fifth Cohort advancing in turtle formation, shields forming a shell over their heads and sides.

From "The Son of Neptune" by Rick Riordan

Related Words

• affluent
• booming
• comfortable
• flourishing
• fortunate
• rich
• robust
• wealthy
• well-heeled
• well-off
• well-to-do