What of it?
Definition 1 of 1
Pro Tip 1/3Defensive Response
Used when someone feels attacked or criticized, to show they don't think there's a problem. 
"They said your work is sloppy." "What of it? It's still effective."
Pro Tip 2/3Casual Dismissal
Indicates casual dismissal of a topic, often because the speaker finds it trivial or irrelevant. 
"You spilled your drink!" "What of it? It's just water."
Pro Tip 3/3Provokes more debate
Can invite further questions or exacerbate a dispute, so use it when you're willing to discuss more. 
"This plan seems risky." "What of it? Are you suggesting a better one?"