1.nounAn entity exhibiting high class especially through refinement of demeanor, conscientiousness of behavior, and/or skillfulness in performance; or an exhibition of high class especially of one or more of those types:
2.nounUsed sarcastically, a person, entity, event, or action entity exhibiting the opposite of the above characteristics, i.e., boorish, unprincipled, and/or bungling behavior
"Did you hear about Peter's "milk-milk-lemonade" toast to Lois at their wedding reception? After a class act like that, I'm surprised that anyone in the Pewterschmidt family is still speaking to him."