"prethalamus" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "pre",
        "3": "thalamus"
      },
      "expansion": "pre- + thalamus",
      "name": "prefix"
    }
  ],
  "etymology_text": "pre- + thalamus",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "prethalamus",
      "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": "other",
          "name": "English terms prefixed with pre-",
          "parents": [],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": "prethalamic"
        }
      ],
      "glosses": [
        "Synonym of subthalamus"
      ],
      "id": "en-prethalamus-en-noun-v3kmuMR4",
      "links": [
        [
          "subthalamus",
          "subthalamus#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "subthalamus"
        }
      ]
    }
  ],
  "word": "prethalamus"
}

{
  "derived": [
    {
      "word": "prethalamic"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "pre",
        "3": "thalamus"
      },
      "expansion": "pre- + thalamus",
      "name": "prefix"
    }
  ],
  "etymology_text": "pre- + thalamus",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "prethalamus",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English nouns with unknown or uncertain plurals",
        "English terms prefixed with pre-"
      ],
      "glosses": [
        "Synonym of subthalamus"
      ],
      "links": [
        [
          "subthalamus",
          "subthalamus#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "subthalamus"
        }
      ]
    }
  ],
  "word": "prethalamus"
}