what's the idea

Idioms  

1. 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.

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Example Sentences

In a tweet on Thursday morning, the pub chain asked the retailer "what's the idea with these T-shirts!?"

From BBC • Apr. 13, 2023

Nobody had done it before, so what’s the idea?

From Los Angeles Times • Jun. 2, 2021

“So what’s the idea? That afterwards you and I have the exact same conversation?”

From The Verge • May 14, 2018

“I wasn’t. But what’s the idea of a hospital without a doctor?”

From "A Farewell To Arms" by Ernest Hemingway

And what's the idea of the private ship?

From Astounding Stories of Super-Science, November, 1930 by Various