to indulge in inappropriate daydreaming about someone (or something), generally with sexual intent.
- Girl 1: I saw you playing pocket pool during class!
- Girl 2: oh yeah, I initially sat in the front to get a good grade, but I ended up fucktasizing about the teacher the whole time.
- Girl 1: Yea, oh yea.
- Guy 1: I got stoned last night and ended up getting the most epic ass munchies ever, but I didn't have any food in the house. I got desperate and ended up fucktasizing about apple pie and like 20 KFC double downs.
- Guy 2: Doooooood.