lose one's marbles

idiom

Definition of lose one's marbles

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.

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“Lose one's marbles.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lose%20one%27s%20marbles. Accessed 31 Oct. 2020.

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