A few definitions:
Graham Bell, The Permaculture Way
Permaculture is the conscious design and maintenance of agriculturally productive systems which have the diversity, stability, and resilience of natural ecosystems. It is the harmonious integration of the landscape with people providing their food, energy, shelter and other material and non-material needs in a sustainable way.
Simon Henderson, Cortez IS, BC
Permaculture is the use of ecology as the basis for designing integrated systems of food production, housing appropriate technology and community development. It offers a practical, creative approach to the problems of diminishing resources and threatened life support systems now facing the world.
Guy Baldwin, Cortez Is, BC
Permaculture is a holistic approach to landscape design and human culture. It is an attempt to integrate several disciplines, including biology, ecology, geography, agriculture, architecture, appropriate technology, gardening and community building.