The legendary grade of myth given by teachers to those students demonstrating a level of suck beyond imaginable. Acquiring an F minus for a grade is such a feat beyond the norm that this student must be beyond hope.
Such a feat as acquiring an F- is not an easy gain, and the everyday slacker will just not do. To obtain such a legendary grade upon your classroom input, one must work hard and put in thousands upon thousands of samples of ignorance while simultaneously putting in time unworthy of class participation points such as the classic "A for effort".
In most cases, this grade is so beyond fail that it equals win.
Teacher: I called upon you to do your presentation, so you walked to the front of class, sat in my valuable teachers' desk that I paid for with my own money, and managed to break it. Not to mention this is chemistry class, NOT geometry, and doing a demonstration on finding the area of a Pokeball will get you nowhere in life. F-.