Demoniacal describes something wild, uncontrolled, and evil — as if a demon were driving it. A demoniacal laugh, a demoniacal rage, a demoniacal look: the word paints a person or act that has gone past ordinary anger into something frightening and not quite human. Though actually, people almost never use it today because they believe in demons in the room. It is an old, heavy, literary adjective. In modern English, demonic is the more common cousin, and even that is often just a strong way to say “very wild” or “very cruel.” You will meet demoniacal in novels and older writing more than in speech. Using it about a noisy classroom would sound like a joke, or like you were on stage.

惡魔般的、狂暴凶惡的（文學用語）