"terre rare" meaning in French

{
  "forms": [
    {
      "form": "terres rares",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "terre rare f (plural terres rares)",
      "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 2 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "fr",
          "name": "Chemistry",
          "orig": "fr:Chemistry",
          "parents": [
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "rare earth, lanthanide"
      ],
      "id": "en-terre_rare-fr-noun-D1RkIbf3",
      "links": [
        [
          "chemistry",
          "chemistry"
        ],
        [
          "rare earth",
          "rare earth"
        ],
        [
          "lanthanide",
          "lanthanide"
        ]
      ],
      "raw_glosses": [
        "(chemistry) rare earth, lanthanide"
      ],
      "synonyms": [
        {
          "word": "lanthanide"
        }
      ],
      "tags": [
        "feminine"
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/tɛʁ ʁaʁ/"
    }
  ],
  "word": "terre rare"
}

{
  "forms": [
    {
      "form": "terres rares",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f"
      },
      "expansion": "terre rare f (plural terres rares)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "French countable nouns",
        "French entries with incorrect language header",
        "French feminine nouns",
        "French lemmas",
        "French multiword terms",
        "French nouns",
        "French nouns with red links in their headword lines",
        "French terms with IPA pronunciation",
        "Pages with 2 entries",
        "Pages with entries",
        "fr:Chemistry"
      ],
      "glosses": [
        "rare earth, lanthanide"
      ],
      "links": [
        [
          "chemistry",
          "chemistry"
        ],
        [
          "rare earth",
          "rare earth"
        ],
        [
          "lanthanide",
          "lanthanide"
        ]
      ],
      "raw_glosses": [
        "(chemistry) rare earth, lanthanide"
      ],
      "synonyms": [
        {
          "word": "lanthanide"
        }
      ],
      "tags": [
        "feminine"
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/tɛʁ ʁaʁ/"
    }
  ],
  "word": "terre rare"
}