mustn't

contraction

: must not

Word History

First Known Use

1739, in the meaning defined above

Time Traveler
The first known use of mustn't was in 1739

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Cite this Entry

“Mustn't.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mustn%27t. Accessed 27 Feb. 2025.

Kids Definition

mustn't

: must not
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