must not

• mustn't

must not (third-person singular simple present must not, no present participle, no simple past or past participle)

1. Used to indicate that something is forbidden.

   Pedestrians must not cross the road until the light goes green.

   Synonyms: must refrain from, be not to

Although must and have to are synonymous, there is a distinction in English between must not (indicating proscription) and not have to (indicating a lack of necessity).

• muttons