He is a 'madman' out on the ski slopes. [=he is an extremely daring or reckless skier]
He drives 'like a madman'. [=he drives very recklessly]
a celebrity being stalked by a 'madman'
(..) He clocks it, you know. High! Fly ball down the left field line! people on their feet yellin' at the ball. But that's nothin', 'cause Fisk, he's wavin' at the ball like a madman. - You know, "Get over! Get over!" - Yeah, I've seen that. Right. Right. "Get over!" And then it hits the foul pole. (..)1997 Good Will Hunting