Bill's Definition: Permaculture is a design system for creating sustainable human enviroments. Bill Mollison, Introduction to permaculture Tagari press- 1991
Permaculture is the conscious design and maintenance of agriculturally productive ecosystems which have the diversity , stability  and resilience of natural ecosystems. Permaculture-A Designers manual. Tagari press-1988

David’s Definition: "Consciously designed landscapes which mimic the patterns and relationships found in nature, while yielding an abundance of food, fibre nad energy for provision of local needs" David Holmgren, Permaculture Principles & Pathways Beyond Sustainability-2002
This book details a sensible design approach to a declining fossil fuel future.

Peter’s view on Permaculture: is that its about designing self regulating and sustainable systems for food production, materials and other needs of humans and their animals that takes into account and facilitates a net decrease in the earths resources needed to sustain the system and an increase in the yields for humans.
My tiny contribution to Permaculture is to take the learning from 30 odd courses with the  experience Silvia & I have gained on multiple small farms across Victoria and the travels around the world looking at simple agriculture systems and communities and use all this to help some local people on their initial jorney down the Permaculture road to the future.
Instead of being fancy I would rather supply simple useable information and training with practical experience to willing participants, this means simple workshops & short courses and the PDC along with farm tours.