If I click on "share definition" after I edit a definition, is that going to change the definition everyone sees or is that just going to provide an alternate definition available upon clicking?

It will submit it as a correction for Chris to review--if he accepts it, then everyone will see it. Until he gets to it, it's just your custom definition. Even if he doesn't accept it, you get to keep it.

Thanks for helping edit our definitions!

oh okay, cool! Thanks Nick