When something bad could occur after making a plan, a person usually says this in a sarcastic way. Mainly used in Ireland.
Person 1: Hey, do you want to rob this persons house tonight?
Person 2: Yeah, but there is a lot of security so there's a chance we'll get caught.
Person 1: what harm!
What harmful effects could happen when a metal mixes with acids?
What harmful effects could happen when a metal mixes with acids?