lose one's marbles
idiom
informal + humorous
: to become insane
When he started ranting about how the government was out to get him, I thought he'd lost his marbles.
Cite this Entry
“Lose one's marbles.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lose%20one%27s%20marbles. Accessed 25 May. 2025.
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Merriam-Webster unabridged
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