n. The anointed successor to MS-DOS for Intel 286- and 386-based micros; proof that IBM/Microsoft couldn't get it right the second time, either. Mentioning it is usually good for a cheap laugh among hackers -- the design was so baroque, and the implementation of 1.x so bad, that 3 years after introduction you could still count the major apps shipping for it on the fingers of two hands -- in unary. Often called 'Half-an-OS'. On January 28, 1991, Microsoft announced that it was dropping its OS/2 development to concentrate on Windows, leaving the OS entirely in the hands of IBM; on January 29 they claimed the media had got the story wrong, but were vague about how. It looks as though OS/2 is moribund.
See vaporware, monstrosity, cretinous, second-system effect.