A widespread consensus on a particular product or protocol which has not been ratified by any official standards body, such as ISO, but which nevertheless has a large market share. The archetypal example of a de facto standard is the IBM PC which, despITe is many glaring technical deficiencies, has gained such a large share of the personal computer market that IT is now popular simply because IT is popular and therefore enjoys fierce competITion in pricing and software development. (1994-10-27)