If you describe someone's behaviour as maniacal, you mean that it is extreme, violent, or very determined, as if the person were insane.
例句
He was almost maniacal in his pursuit of sporting records...他近乎发疯般地追求着打破体育纪录。She is hunched forward over the wheel with a maniacal expression.她弓身伏在方向盘前，表情像疯了一样。