plaid screen definition, from Internet Connection, Inc.

[XEROX PARC] A ‘special effect’ that occurs when certain kinds of memory smashes overwrite the control blocks or image memory of a bit-mapped display. The term “salt and pepper” may refer to a different pattern of similar origin. Though the term as coined at PARC refers to the result of an error, some of the X demos induce plaid-screen effects deliberately as a display hack.