めっ
1
interjection (kandoushi)
no!;don't!;tsk!
used to scold small children and pets
ただし、学生の本分は学業ですから、期末テストをおろそかにしたらメッ！ですよ？
However, the duty of a student is to study. So if you neglect the end of term test, that's a "no!".