imo. unschooling is learning thru life. Viewing education as the stuff everyday life is made of, not following a set curriculum, letting your child decide what, when ,and how to learn.
I once read someone describing it, as "imagine every day as summer vacation" or st like that,
As Ms. Frizzle says from magic school bus, "take chances, make mistakes, get messy!" (this is our motto btw!)
Unschooling doesn't mean that you never use traditional study materials, but that you use them when your child expresses and interest in learning abt st.
Unschooling isn't lazy, to the contrary you need to have an active, full interesting life full of field trips, tons of books, ect to spark the childs interest in things, and then you just go off from there.
It is trusting your child to learn what he needs to learn, when he needs to learn it.
Hope this helps a little, I agree unschooling .com is an excellent resource, and can help you define it better.