名词
1. 疯子;狂人
A maniac is a mad person who is violent and dangerous.
2. 极其愚蠢的;疯狂的
If you describe someone's behaviour as maniac, you are emphasizing that it is extremely foolish and uncontrolled.
3. (宗教或体育的)狂热分子，过激分子
If you call someone, for example, a religious maniac or a sports maniac, you are critical of them because they have such a strong interest in religion or sport.