No, before you ask, it does not refer to a
sexy teacher who wants to fuck his/her students.
1. It refers to a teacher who gives
a shitload of homework. This homework will either be
exploration homework (you have to do something that wasn't taught to you) or repetitive busywork.
2. It refers to a teacher who comes into class, reads from his/her notes, and gives you a problem to work on for an hour with no input from the teacher at all. A related concept would be busywork.
3. It refers to a teacher who grades his/her favorite students a full letter grade higher than his/her least favorite students, just because he/she can.
4. It refers to a teacher who likes to
examine tests and essays too closely.
5. It refers to a teacher who doesn't look at assignments closely enough.
6. Last but not least, it refers to a bad teacher who reads this definition and does not realize that he/she is an asshole.