Minatory means threatening. When you petition the school for higher academic standards––i.e. harder grading from teachers––you may receive some minatory looks, or even hate notes, from the kids in your school.
Minatory derives from the Latin menatorius, "menace," and has nothing at all to do with the Greek legends of the Minotaur. But think of the Minotaur anyway––it was half-man, half-bull, lived inside a labyrinth, and could only be appeased if it was being sent young women to devour. If that's not threatening, or minatory, behavior, nothing is.