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what's the big idea

idiom

informal
—used to ask why someone is doing or saying something
Hey! What's the big idea!?

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what's the big deal?
what's the big idea
what's the difference?
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“What's the big idea.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/what%27s%20the%20big%20idea. Accessed 2 Dec. 2025.

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