1. When your ass just doesn't look good in anything , skirts , jeans , dresses. ANYTHING. Mainly affects women but gay and metrosexual men also suffer from it time to time.
2. When you don't want to be a nice guy and instead for just a day , turn into a badass. A bad ass day can starts from when you wake up to when you go to sleep , you may also have experience baddass dreams that night.
1. "My ass looked horrible yesterday . not even that weird Persian ghuy checked me out. It was the worst bad ass day"
Oscar - "Was there any reason that you killed Mrs Porter's cat yesterday?"
Pete - "I was having a bad ass day"
Oscar - "Yeah I'm pretty sure the cops aren't going to take that into account".