I would be glad if the formula didn't require variation, because then I could show some authority for my sort of definition. However the words "greater then", are obviously a reference to variation, otherwise the formulation would not make sense. I'm afraid that when I would argue some professional biologist, I would likely be called a liar for saying that definition referred doesn't require variation. Again, most biologists I talked to explicitly deny Natural Selection without variation is valid.
They are of course not the same definitions, one requires variation, the other doesn't. One involves a comparison on genotype/allelle the other doesn't. That you make no argumentation which definition is better, just shows to me you are trying to find an easy way out without actually making sound argument.
Would you really not object if you found the short definition that didn't require variation to apply was in a dictionary or glossary?
regards,
Mohammad Nor Syamsu