If we are sitting here trying to define luck...then we should be able to apply it to everything. Using your words you said "it is measured by how likely and how often you are able to do that one thing". You used that notion to back your case. Why can't I use it to back mine? If what you said is what you meant, then a fighter with a smaller % of victory beating a fighter with a higher % (or probability) of victory...is luck...or lucky.
Bottom line is it is not. You know this and I know this. It isn't because 2 pro fighters are in there with tons of practice behind them. Some fighters have off nights. Some have good nights.
GSP may have had an off night. Matt Serra may be lucky to have caught GSP on his "off night" (again fighters aren't machines)...but taht actual punch and result wasn't luck.
With this logic...If GSP finishes anyone in the next 5 years, he will have been lucky. Because these days it is not probable. If he finishes Condit it would be LUCK because Condit rarely gets finishes and GSP rarely finishes. Would this example be correct? Or do we want to cherry pick scenarios some more?
And I agree with your last point. I never said there was no ounce of luck in this. I said Luck in no way out-weighs skill in terms of a fighter KOing another. May be luck in the other defense and timing...but it was skill and practice to do it. Luck is few and far between in this sport.
If GSP came out and casually knocked out Condit, yes, I would consider that to be lucky.
We all seem to have different interpretations of what actually constitutes as luck though, so we're not getting any where.
We'll have to agree to disagree.