from the GNU version of the Collaborative International Dictionary of English
- A bar, connected with a switch, longer than the distance between any two consecutive wheels of a train (45 to 50 feet), laid inside a rail and operated by the wheels so that the switch cannot be thrown until all the train is past the switch.
from The Century Dictionary and Cyclopedia
- n. A secondary rail or bar placed beside the rails of a switch and intended to prevent its movement while a train is passing over it.
Sorry, no etymologies found.