Simple Definition of third rail
: a metal rail on a train track that carries electric current to the train's motor
: a difficult issue that politicians try to avoid talking about
Full Definition of third rail
1 : a metal rail through which electric current is led to the motors of an electric vehicle (as a subway car)
2 : a controversial issue usually avoided by politicians
Examples of third rail in a sentence
Social Security is the third rail of American politics.
First Known Use of third rail
Learn More about third rail
Britannica.com: Encyclopedia article about third rail
Seen and Heard
What made you want to look up third rail? Please tell us where you read or heard it (including the quote, if possible).