The third rail on a railroad track is the steel bar which passes electric current to a train.
2. singular noun [theN]
If you refer to something as thethird rail of a political situation, you mean that it would be dangerous to make changes tothat thing because people feel very strongly about it.
[US]
Politicians speak of Social Security as the third rail. To touch it is to commitpolitical suicide.
third rail in British English
noun
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. US politics
a.
a cause or topic that is considered extremely dangerous for a person to support or comment on
b.
(as modifier)
a third-rail issue
third rail in American English
US
an extra rail used in some electric railways, instead of an overhead wire, for supplying power
Examples of 'third rail' in a sentence
third rail
He could see it there, down on the tracks, by the third rail: a small splash of purple, his troll.