Refers to a formula developed by Bill James, the noted baseball sabermetrician, to predict outcomes. Most baseball sims rely on some version of the formula. Here are some useful links.
Prior to Version 7.0 we relied exclusively on the Original Version of the Formula. But beginning with the 7.0 release we are using either the Morey Z Version--which mitigates against extremes and statistical 'outliers'--or a hybrid of Morey Z with the Original.