My take on the definition of wild camping is:
Self reliant, taking in all that you need except renewable resources taken from your immediate environment. (dead wood, hazel wands for pot stands etc.)
The site chosen should be remote from civilisation, be it on hills, in valleys or woods.
When wild camping it is important to leave no trace of your being there. Remove all rubbish and fully extinguish fires and erradicate signs of them.
The essence of wild camping is freedom to stop and set up camp where you see fit. It brings with it the responsibility of leaving the enviromnet where you camped as it was prior to your visit.
I cannot remember where I heard the quote "Take only photographs, leave only footprints".
Stewey.