View synonyms for third rail

third rail

[ thurd reyl ]


  1. Railroads.
    1. a rail laid parallel and adjacent to the running rails of an electrified railroad to provide electric current to the motors of a car or locomotive through contact shoes.
    2. an additional running rail laid on the same ties as the two regular rails of a railroad track to provide a multigauge capability.
  2. a controversial topic or issue in the public sphere that people, especially politicians, try to avoid discussing (often used attributively): Doping is the third rail of the Olympics.

    a third-rail subject;

    Doping is the third rail of the Olympics.

    Social Security is the third rail of American politics.

third rail


  1. an extra rail from which an electric train picks up current by means of a sliding collector to feed power to its motors
  2. politics
    1. a cause or topic that is considered extremely dangerous for a person to support or comment on
    2. ( as modifier )

      a third-rail issue

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Word History and Origins

Origin of third rail1

An Americanism dating back to 1865–70
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Idioms and Phrases

Something that is dangerous to tamper with, as in Anything concerning veterans is a political third rail . This term alludes to the rail that supplies the high voltage powering an electric train, so called since 1918. On the other hand, grab hold of the third rail means “become energized.” Both shifts from the original meaning date from the late 1900s.
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Example Sentences

That is to say, exactly the type of person to grasp this particular third rail.

Some of the other controversial solutions you touch on in the book, such as geoengineering and nuclear power, are third rail topics in the environmental sphere.

From Time

Cars floated in the streets, one third rail caught fire within a subway station, water poured into apartments.

If entitlement reform is the third rail of politics, this is an entire third-rail transportation system.

And then there is the third-rail issue that is particularly electric in a state with so many retirees.

Marriage equality is not remotely the third-rail issue it is sometimes considered.

The third-rail system in its simplest form is shown in Fig. 29, which represents a section through the roadbed.

They had traveled by the third-rail line twenty miles into the country.

A great rate of speed can be gained with the third-rail system, ten miles having been made in thirteen and a half minutes.

It was originally on the third-rail system, but was changed into an ordinary overhead trolley seven or eight years ago.

He may perfect a third-rail system for use on moving trains.


Definitions and idiom definitions from Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.




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