"must not" meaning in English

{
  "forms": [
    {
      "form": "must not",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~",
        "2": "-",
        "3": "-"
      },
      "expansion": "must not (third-person singular simple present must not, no present participle, no simple past or past participle)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Czech translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with French translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Welsh translations",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "Pedestrians must not cross the road until the light goes green.",
          "type": "example"
        }
      ],
      "glosses": [
        "Used to indicate that something is forbidden."
      ],
      "id": "en-must_not-en-verb-FbxZdw8e",
      "links": [
        [
          "forbidden",
          "forbidden#English"
        ]
      ],
      "synonyms": [
        {
          "word": "must refrain from"
        },
        {
          "word": "be not to"
        },
        {
          "word": "mustn't"
        }
      ],
      "tags": [
        "no-past",
        "no-present-participle",
        "participle",
        "past"
      ],
      "translations": [
        {
          "code": "cs",
          "lang": "Czech",
          "sense": "must refrain from",
          "word": "nesmět"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "must refrain from",
          "word": "devoir ne pas"
        },
        {
          "code": "cy",
          "lang": "Welsh",
          "sense": "must refrain from",
          "word": "bod rhaid i ... beidio â"
        },
        {
          "code": "cy",
          "lang": "Welsh",
          "sense": "must refrain from",
          "word": "gorfod peidio â"
        }
      ]
    }
  ],
  "word": "must not"
}

{
  "forms": [
    {
      "form": "must not",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~",
        "2": "-",
        "3": "-"
      },
      "expansion": "must not (third-person singular simple present must not, no present participle, no simple past or past participle)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English auxiliary verbs",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms with usage examples",
        "English verbs",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Czech translations",
        "Terms with French translations",
        "Terms with Welsh translations"
      ],
      "examples": [
        {
          "text": "Pedestrians must not cross the road until the light goes green.",
          "type": "example"
        }
      ],
      "glosses": [
        "Used to indicate that something is forbidden."
      ],
      "links": [
        [
          "forbidden",
          "forbidden#English"
        ]
      ],
      "synonyms": [
        {
          "word": "must refrain from"
        },
        {
          "word": "be not to"
        }
      ],
      "tags": [
        "no-past",
        "no-present-participle",
        "participle",
        "past"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "mustn't"
    }
  ],
  "translations": [
    {
      "code": "cs",
      "lang": "Czech",
      "sense": "must refrain from",
      "word": "nesmět"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "must refrain from",
      "word": "devoir ne pas"
    },
    {
      "code": "cy",
      "lang": "Welsh",
      "sense": "must refrain from",
      "word": "bod rhaid i ... beidio â"
    },
    {
      "code": "cy",
      "lang": "Welsh",
      "sense": "must refrain from",
      "word": "gorfod peidio â"
    }
  ],
  "word": "must not"
}