None of the things you quoted state that gauging is a proper term to use**
Also gauging does not 'mean to gauge ones ears' because A. you can't use the term in the definition, and B. if anything it means to 'gauge any piercing' because clearly I 'gauged my lip ring' even though gauging isn't the proper term, and I didn't even stretch it.
I think pretty much everyone knows gauging is a word.
Estimate or determine the magnitude, amount, or volume of.
Form a judgment or estimate of (a situation, mood, etc.)
That is the definitions by the dictionary. You will now rebut that you meant about piercings but you literally said "gauging is not a word."