"palatal expander" meaning in English

{
  "forms": [
    {
      "form": "palatal expanders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "palatal expander (plural palatal expanders)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Dentistry",
          "orig": "en:Dentistry",
          "parents": [
            "Medicine",
            "Teeth",
            "Biology",
            "Sciences",
            "Mouth",
            "All topics",
            "Face",
            "Fundamental",
            "Head and neck",
            "Body parts",
            "Body",
            "Anatomy",
            "Human"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A device used to widen the upper jaw so that the bottom and upper teeth will fit together better."
      ],
      "id": "en-palatal_expander-en-noun-2HM7y30r",
      "links": [
        [
          "dentistry",
          "dentistry"
        ]
      ],
      "raw_glosses": [
        "(dentistry) A device used to widen the upper jaw so that the bottom and upper teeth will fit together better."
      ],
      "topics": [
        "dentistry",
        "medicine",
        "sciences"
      ],
      "wikipedia": [
        "palatal expander"
      ]
    }
  ],
  "word": "palatal expander"
}

{
  "forms": [
    {
      "form": "palatal expanders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "palatal expander (plural palatal expanders)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Dentistry"
      ],
      "glosses": [
        "A device used to widen the upper jaw so that the bottom and upper teeth will fit together better."
      ],
      "links": [
        [
          "dentistry",
          "dentistry"
        ]
      ],
      "raw_glosses": [
        "(dentistry) A device used to widen the upper jaw so that the bottom and upper teeth will fit together better."
      ],
      "topics": [
        "dentistry",
        "medicine",
        "sciences"
      ],
      "wikipedia": [
        "palatal expander"
      ]
    }
  ],
  "word": "palatal expander"
}