Officers of the U.S. Air Forces, ending their first year in Britain, had learned combat lessons from the Royal Air Force. They had also learned a new lingo.
Even the U.S. War Department took cognizance of British flyers' slang, solemnly announcing that "rhubarb" means "a target of opportunity." When a fighter pilot flies low over France, strafing whatever he finds trains, troops, airdromes he is "on a rhubarb."
How much R.A.F. slang will seep into the dictionary is a lexicographer's guess, but some of its catchier terms have already been adopted by groundlings. Among thousands of Americans, "browned off" already...