1. third rail - Noun
2. third rail - Phrase
The electrified rail that runs beside or between train tracks to power electric trains.
(by extension) Anything that is dangerous to come into contact with, or is best avoided.
Source: en.wiktionary.orgI gave him a kick and he stepped back onto the third rail. Exploding, flaming eraser! This is why moms tell you to stay away from the third rail, but it sure came in handy this time. James Patterson
I hit the third rail. You cannot criticize Israel in this country and survive. Helen Thomas
Barbecue is the third rail of North Carolina politics. John Shelton Reed
It's a matter of invitations versus context. Twitter is really good at providing context, like, I'm having coffee at Third Rail Coffee.' Foursquare is about invitations to places. In this respect Foursquare has started to replace Yelp for me. Jack Dorsey
I am going to give the American people a huge helping of unbridled truth: that we can't continue to spend what we are spending, that we can't avoid entitlement reform because we are afraid of third rail politics. Rick Perry
It means the third rail has seven hundred volts of direct current running through it. Touch it and you're human popcorn. James Patterson