Third rail

What is Third rail?

Third rail definition and meaning on Dictionary terms:
noun

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.
a controversial topic or issue in the public sphere that people, especially politicians, try to avoid discussing (often used attributively): a third-rail subject;Doping is the third rail of the Olympics.Social Security is the third rail of American politics.