YOU are seated on a Florida-bound airplane, reading a magazine at 35,000 feet. Suddenly the plane encounters turbulence, and the flight attendant makes a hasty announcement: "Ladies and gentlemen, the captain has illuminated the seat-belt sign."Illuminated? Over the scratchy public-address system, the word sounds like eliminated, which would give everyone permission to get up and move around. But you know what she means, and you dutifully buckle up. Later, as the plane taxis to the gate after landing in Tampa, another flight attendant tells her captive audience that although the flight will continue to Cancun, "Everyone must deplane the aircraft here so the equipment can be serviced." If the driver of a car were to tell his passengers to "decar the automobile," he would almost certainly get funny looks. But when someone in a uniform delivers double talk about deplaning an aircraft, no one seems to notice. Airlines are hardly the only guilty parties, of course. For a while, one major hotel chain greeted callers on its toll-free number with a recording that began, "Our reservation lines are momentarily occupied." Call it "overspeak the corporate tendency to use pretentious, polysyllabic words when simpler ones will do. While taste in other areas has tended to go clean and functional, certain kinds of language have become more rococo, full of frills and unnecessary elaborations. Think of it as the linguistic equivalent of chrome tail fins on cars. Think of it as putting on airs. Inflated language takes many forms. Several years ago, a car salesman handed me a business card listing his title as "Transportation Expert." Janitors have christened themselves building maintenance engineers, and garbage collectors have metamorphosed into sanitation engineers. Then there are the flowery names developers invent for middle-class subdivisions to make them sound like home-sweet-home for the landed gentry. From Park Forest Meadows to Carriage Hills Estates, the pseudo-snob appeal escalates. On one level, this excess verbiage seems comic - a harmless attempt to create an aura of importance or self-importance. But just as grade inflation changes the scale by which students are measured, word inflation subtly alters the value of language. Overwrought rhetoric creeps into every area of life, even contributing to functional illiteracy when it involves the written word. Who has not puzzled over an income tax form or a manual explaining how to use a computer or put together a toy? "Some assembly r equired" may be one of the most frustrating phrases in the English language. The shrill use of metaphors can be equally irresponsible. It is insulting as well as careless to use the term holocaust casually. A letter writer to the Boston Globe points out another case of linguistic abuse when she complains about an earlier letter writer's facile misappropriation of the word rape. "I agree that we have been supremely ripped off by Keating and the rest of the savings and loan scammers," she writes, "but let's get real: We have not been raped; we've been robbed." The failure to say things straight manifests itself in an opposite extreme: "underspeak the corporate habit of hiding an economic catastrophe behind comforting euphemisms. This year's favorite description of hasty retreat is "restructuring" or "streamlining." One automotive analyst described the decision by General Motors to close 11 plants and lay off 74,000 employees as a need to "lean out" the company's operations. To those being "leaned out," the phrase hardly does justice to the anguish. If the excess of the '80s gives way to a new austerity in the '90s, will language "lean out" too? You'll know for sure when a recorded voice tells you that a reservation line is busy rather than momentarily occupied and when a flight attendant explains that the captain has turned on - not illuminated - the seat-belt sign. Until then, follow the commands given by the leaders of overspeak: Stay on the line, because a reservation agent will be available to assist you shortly. Keep your seat belt fastened. And never, ever deplane until the captain has brought the aircraft to a full and complete stop at the gate.