"grand jour" meaning in French

{
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-"
      },
      "expansion": "grand jour m (uncountable)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "French entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "big day (a day on which something significant happens)"
      ],
      "id": "en-grand_jour-fr-noun-vDMKavPg",
      "links": [
        [
          "big day",
          "big day"
        ]
      ],
      "related": [
        {
          "word": "jour à marquer d’une pierre blanche"
        },
        {
          "word": "heure de vérité"
        },
        {
          "english": "in broad daylight",
          "word": "au grand jour"
        }
      ],
      "tags": [
        "masculine",
        "uncountable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɡʁɑ̃ ʒuʁ/"
    }
  ],
  "word": "grand jour"
}

{
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-"
      },
      "expansion": "grand jour m (uncountable)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "related": [
    {
      "word": "jour à marquer d’une pierre blanche"
    },
    {
      "word": "heure de vérité"
    },
    {
      "english": "in broad daylight",
      "word": "au grand jour"
    }
  ],
  "senses": [
    {
      "categories": [
        "French entries with incorrect language header",
        "French lemmas",
        "French masculine nouns",
        "French multiword terms",
        "French nouns",
        "French terms with IPA pronunciation",
        "French uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "big day (a day on which something significant happens)"
      ],
      "links": [
        [
          "big day",
          "big day"
        ]
      ],
      "tags": [
        "masculine",
        "uncountable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɡʁɑ̃ ʒuʁ/"
    }
  ],
  "word": "grand jour"
}