Better late than never, here's a definition (an explanation but not a
definition had been given in response to the inquiry):
Extropy is the extent of a system’s intelligence, information, vitality,
diversity, and capacity for improvement.
Max
Max More, Ph.D.
more@extropy.org
http://www.primenet.com/~maxmore
President, Extropy Institute: exi-info@extropy.org, http://www.extropy.org