"charbons fossiles" meaning in Français

{
  "categories": [
    {
      "kind": "other",
      "name": "Formes de locutions nominales en français",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Français",
      "orig": "français",
      "parents": [],
      "source": "w"
    }
  ],
  "forms": [
    {
      "form": "charbon fossile",
      "tags": [
        "singular"
      ]
    }
  ],
  "lang": "Français",
  "lang_code": "fr",
  "pos": "noun",
  "pos_title": "Forme de locution nominale",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Exemples en français",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              4,
              21
            ]
          ],
          "ref": "Denis Diderot, Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts et des Métiers, Tome troisième, 1753, p. 190",
          "text": "Les charbons fossiles de la première espèce se trouvent profondément en terre."
        }
      ],
      "form_of": [
        {
          "word": "charbon fossile"
        }
      ],
      "glosses": [
        "Pluriel de charbon fossile."
      ],
      "id": "fr-charbons_fossiles-fr-noun-3dM0x-Uw"
    }
  ],
  "sounds": [
    {
      "ipa": "\\ʃaʁ.bɔ̃ fɔ.sil\\"
    }
  ],
  "tags": [
    "form-of",
    "masculine"
  ],
  "word": "charbons fossiles"
}

{
  "categories": [
    "Formes de locutions nominales en français",
    "français"
  ],
  "forms": [
    {
      "form": "charbon fossile",
      "tags": [
        "singular"
      ]
    }
  ],
  "lang": "Français",
  "lang_code": "fr",
  "pos": "noun",
  "pos_title": "Forme de locution nominale",
  "senses": [
    {
      "categories": [
        "Exemples en français"
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              4,
              21
            ]
          ],
          "ref": "Denis Diderot, Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts et des Métiers, Tome troisième, 1753, p. 190",
          "text": "Les charbons fossiles de la première espèce se trouvent profondément en terre."
        }
      ],
      "form_of": [
        {
          "word": "charbon fossile"
        }
      ],
      "glosses": [
        "Pluriel de charbon fossile."
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "\\ʃaʁ.bɔ̃ fɔ.sil\\"
    }
  ],
  "tags": [
    "form-of",
    "masculine"
  ],
  "word": "charbons fossiles"
}