what is the ovality

It's a measure of how far off circularity you are. The usual way to find it is to measure the major diameter (call that Fred). Then measure the minor diameter (call that Ethel). The formula is then

(2(Fred - Ethel)/(Fred + Ethel)) x 100%

Cheers.

You have not stated exactly what you are talking about the "ovality" of (some sort of pipe, tube, cylinder, rod, etc., nor to what sort of code or standard in what area you might be expecting the definition to conform??)

I say this in that there might not be just one universal or unchallenged definition (agreed to by all in all fields/areas) of "ovality", nor for that matter also "out-of-roundness", without further explaining in breakdown/terms understood by all exactly what is meant.

Therefore in my opinion, whenever such terms are presented e.g. in a specification or drawing etc. one should also represent what they are talking about in algebraic/ formula terms, replete with unambiguous definitions also any variables of same (as the previous responder has provided one such formula, I suspect indeed applicable to some field), or a standard/code should be referred to that provides such unambiguous formula.