Christian- I said that blurring will definitely make any rigorous definition impossible. The superficial A380 damage is probably accident because of the nature and importance of the event. However in my training days, I indvertently took off with 6 inches (OK- 15 cms for you!) of seat belt with a large metal buckle on the end hanging outside the door opposite on a Cherokee. At lift off it started flailing damaging the fuselage (nothing like the damage the sound did to my nerves- I thought the wing was falling off). Certainly not an accident- only an incident. There will always be this area where they blur together. But I think a large part of the definition is 'how important was the incident?'. But then, 200 injuries as a 747 takes avoiding action in the air- still only an 'incident'? Any sort of contact- accident.
Not an easy question!