I know I will take a lot of heat for this but, ....
I must say I do not understand why this post is lingering.
There is the legal definition, according to the USBC and, then, there is the ego definition that so many have espoused:
that unless the 11th and 12th frames are clean, the game cannot be considered "clean".
They seem to take the more "ethical", the more "moral" high ground than the legal definition. I'm not sure if this makes them feel they are a better bowler or not. I just do not understand.
If you do feel this way, why not petition the USBC to change the definition; so we all can meet the same standards.
Personally I don't care what the definition is. While I'd like every frame to be clean, if the USBC says someone, I or anyone else, has one, so be it: they define the rules. It is the power we have given them.