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of unsound mind

idiom

law
: mentally ill : not sane
She claims that her father was of unsound mind when he changed his will.

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of unknown origin
of unsound mind
of value
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“Of unsound mind.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/of%20unsound%20mind. Accessed 1 Dec. 2025.

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