Definition

1. Noun:
   • The principal route of a transportation system: The most important or central track, road, or route in a network, such as a railway or highway system.

Usage

• The term "main line" is used to designate the primary artery of travel or transport within a larger system. It is often contrasted with branch lines, sidings, or local routes.

Examples

• Noun:
  • The train was delayed on the main line due to signal failure.
  • Intercity trains always run on the main line, while local services use the branch lines.

Advanced Usage

• "Main line" as a historical term in railroading: In railroad terminology, the main line is the route between major terminals or cities that carries the highest volume of traffic.
  • The company invested millions to electrify its busiest main line.
• Figurative Use: The term can be used metaphorically to describe a primary channel, conduit, or method for anything being distributed.
  • This fiber optic cable is the main line for the country's internet data.

Variants and Related Words

• Mainline (verb, slang): To inject a drug intravenously. (Note: This is a distinct, slang usage derived from the concept of a "main" blood vessel, not the transportation definition).
• Mainliner (noun, slang): A person who injects drugs intravenously.

Synonyms

• Trunk line: A main line of a railway, telephone, or other system.
• Principal route: The most important way or course.
• Artery: A major route in a transportation system.

Notes on Different Meanings

• The primary definition provided here is for "main line" as a noun phrase in transportation contexts.
• A separate, well-known slang meaning exists (as referenced in the context) relating to intravenous drug injection. These are considered homographs (same spelling, different meaning) and should be treated as distinct entries in a comprehensive dictionary. This entry focuses solely on the transportation definition.

Noun

1. the principal route of a transportation system