turncoat definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a person who goes over to the opposite side or party; traitor
Origin: from the notion of a coat worn right side out or inside out, according to circumstances
turncoat definition by American Heritage Dictionary
One who traitorously switches allegiance.