what's the big idea

Phrase
?


 * I heard you been chatting up my girl. What's the big idea?
 * Hey, what's the big idea, you telling everybody I'd left town?
 * Hey, what's the big idea, you telling everybody I'd left town?

Usage notes

 * Although the question can be read as "What is the purpose ('big idea') of what you just said or did?", it is almost exclusively used to object to whatever was just said or done by the hearer.