What's the idea?

What's the idea?

A question that expresses frustration or annoyance about what is happening and asks (at least rhetorically) for the reason or motivation behind it. Now just what's the idea, here? I saw you dancing with some other guy out there! Hey, what's the idea? Why are you wearing my favorite dress? What's the idea, shoving me like that?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

What's the (big) idea?

Inf. Why did you do that? (Usually said in anger.) Please don't do that! What's the idea? Why did you shove me? What's the big idea?
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

what's the idea

Also, what's the big idea; the very idea. What do you think you are doing? What foolishness do you have in mind? For example, What's the idea of taking the car without permission? or You've invited yourself along? What's the big idea? or Take a two-year-old up Mount Washington? The very idea! These phrases, all implying the speaker's disapproval, use idea in the sense of "what one has in mind." The first two date from about 1900; the third is heard more in Britain than America.
See also: idea
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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References in periodicals archive ?
"What's the idea?" "Nothing very much, Dad," Ken replied.
"What's the idea?" he shouted, threatening Bull with a second blow.
What's the idea? Keep criminals' hands in good condition to make fingerprinting easier?
WHAT'S THE IDEA? Duo Boots solves a winter fashion problem for thousands of women who don't conform to high-street leg sizes.
"What's the idea?" "I found something about it, Dad," Matias replied.
"What's the idea?" "I just figured out something on it," Peter replied.
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