Definition of "rail" []

• A bar extending horizontally between supports, as in a fence. (noun)
• A structure made of such bars and supports and forming a barrier or guard; a railing. (noun)
• A steel bar used, usually in pairs, as a track for railroad cars or other wheeled vehicles. (noun)
• The railroad as a means of transportation: goods transported by rail. (noun)
• A horizontal framing member in a door or in paneling. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In the nineteenth century, when people wanted to describe the new transportation technology that went chug-chug-chug, they called the engine an “iron horse” and the rail system “track way” (if they were Dutch) or “rail way” (if they were English) or “iron way” (if they were French, German, or Italian) or “narrow iron lane” (if they were Greek)."
• "The “light” in light rail is short for “light-capacity rail transit,” as opposed to “heavy rail” or “heavy-capacity rail transit” (subways and elevateds)."
• "The bottom of this scope forms a rail, and near the front of the rail is a series of grooves."