When you have watched an excessive amount of the tv-show The Mighty Boosh and can't stop neither watching nor quoting it.
Person 1: So I was watching The Boosh yesterday...but was I REALLY watching The Boosh?
Person 2: Oh god, you are so Booshed.
a word with many meanings, depending how you use it in what context, it either means something really wrong or great.
i booshed that game yesterday, or i totally got booshed by that test today.