You are right about the definition of unschooling - it can be different for different families - there is a even a term called radical unschooling where the whole family basically lives their entire lives with the whole unschooling term or a more traditional unschooling method of the parent leaving various items around the house to peek an interest in a child to do further exploring or you can just let the child set the pace and do what they are interested in or a combo of all of the above
:-) We do most of our learning experiences out and about - growing our own garden, raising butterflies, taking old computers apart, experimenting with rocket building... when he shows an interest in something I try to find everything possible in the community to explore concerning that area and what is cool to watch is that as he is exploring a topic he is interested in, he is reading to learn more about it, he is usually doing some kind of math, history usually gets involved while reading about the subject, art comes along if he wants to make something. So instead of forcing him to sit and do reading time (which was ALWAYS a fight), he will sit and spend an hour reading about computer programming to help him complete a project he is working on. Once you start you will quickly realize which method works best for you...I do want to share that before anyone goes and spends a lot of money purchasing curriculum materials, go pick up a few workbooks at a local bookstore or make some of your own lessons and see how your child handles the whole situation first because you may find that one method works better than another and then you can go order curriculum if you want once you see how it all falls together.