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

Dictionary Entries Near mustn't

Cite this Entry

“Mustn't.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mustn%27t. Accessed 30 Nov. 2024.

Kids Definition

mustn't

: must not
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!