If you speak peremptorily, you speak in a short, sharp way that leaves no room for no. You sound as if you expect people to obey at once. It is not friendly, and it is not polite. Teachers, bosses, and parents sometimes fall into this tone when they are in a hurry or feel they have the right to give orders. The word is fairly formal; in everyday talk people say in a bossy way, or as if they would not take no for an answer. Though actually, it is not quite the same as shouting: the voice can stay quiet and still be peremptory, because the meaning is 'this is decided'.

專斷地、不容分說地