noun
a rail through which electric current is supplied to an electric locomotive
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noun : a metal rail through which current is led to the motors of an electric locomotive — compare running rail
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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.
[1865-70, Amer.]
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third rail noun
A rail carrying electricity to an electrically-powered train
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Main Entry: ↑third
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third rail,
a rail paralleling the ordinary rails of a railroad. It carries a powerful electric current and is used on some railroads instead of an overhead wire. The power is picked up by a device (shoe) that extends out from the locomotive or car and fits over the rail.
–third´-rail´, adjective.
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n. an additional rail supplying electric current, used in some electric railroad systems
■ Informal a subject, esp. Social Security, considered by politicians too dangerous to modify or discuss
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noun [singular]
1 : a metal rail on a train track that carries electric current to the train's motor
2 : a difficult issue that politicians try to avoid talking about
Social Security is the third rail of American politics.
Useful english dictionary. 2012.