A person who is a class act has it together, they have a lot of class in public situations. It can also be used as a diss because you can sarcastically use it to describe someone as podunk.. redneck.. immature.. or downright stupid as hell..
"Those bitches are a real class act because they dont have a life and start stupid shit. Man i wish i was them.. they are so tight, not"
"That ho must be a cut above the rest of us because she thinks that shes hott shit"