Pejorative term for chronic fatigue syndrome, coined in the '80s when people weren't convinced that the disease really existed. Given the population's distate for yuppies, the term spread like wildfire.
At the risk of offending genuine CFS sufferers, I have to say it made lots of sense to doubt the yuppie flu. Consider the evidence: Sudden waves of complaints had come from young, upwardly mobile professionals in high-stress jobs with long hours. They were suffering from a variety of ailments that couldn't be measured or really proven, most of them seemingly side effects of fatigue. They insisted it was a disease, but given the stereotype of yuppies as whiny and self-important, lots of people weren't willing to listen. Heck, even today I'm convinced that lots of hyperambitious, sleep-deprived yupsters convinced themselves they had CFS, being too ashamed or too deep in denial to admit they just needed rest.
Nearly all of the medical community accepts CFS as real today, although it's not well understood and is probably not a single ailment. In some cases, for example, it's a manifestation of Lyme Disease. Famous CFS cases include Harlan Ellison and Keith Jarrett... Better yet, you can read the first-hand testimonials noded in Chronic Fatigue Syndrome.