Definition

1. Noun:
   • A live rail supplying electric current to an electric train: The "third rail" is an additional rail running alongside the main train tracks. It carries the high-voltage electrical power needed to operate electric locomotives or subway cars. Contact with it is extremely dangerous.

Usage Examples

• Noun:
  • The subway system gets its power from a third rail.
  • Maintenance workers must de-energize the third rail before performing repairs on the tracks.
  • A safety fence protects people from accidentally touching the lethal third rail.

Advanced Usage

• Metaphorical Use ("Third Rail of Politics"): This is a common figurative extension. It describes a controversial issue considered so dangerous for politicians to address that touching it is likened to touching the lethal electrical rail.
  • Social Security reform is often called the third rail of American politics.
  • The proposed tax was a political third rail; no candidate wanted to endorse it.

Variants and Related Words

• Conductor rail: A more technical synonym for "third rail."
• Live rail: Another term emphasizing that the rail is electrically charged.
• Fourth rail: Some railway systems (e.g., the London Underground) use a separate fourth rail for the electrical return current.

Synonyms

• Conductor rail
• Contact rail
• Live rail
• Power rail

Idioms and Fixed Phrases

• The third rail of [a topic/field]: An idiom denoting an untouchable, highly charged, and potentially career-ending issue within a specific context.
  • In the company, questioning the founder's decisions is the third rail of management.
  • For that committee, budget cuts are the third rail.

Noun

1. a rail through which electric current is supplied to an electric locomotive