"sea chestnut" meaning in English

{
  "forms": [
    {
      "form": "sea chestnuts",
      "tags": [
        "plural"
      ]
    }
  ],
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      "args": {},
      "expansion": "sea chestnut (plural sea chestnuts)",
      "name": "en-noun"
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
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        {
          "kind": "lifeform",
          "langcode": "en",
          "name": "Sea urchins",
          "orig": "en:Sea urchins",
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            "Echinoderms",
            "Animals",
            "Lifeforms",
            "All topics",
            "Life",
            "Fundamental",
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        }
      ],
      "glosses": [
        "A sea urchin."
      ],
      "id": "en-sea_chestnut-en-noun-mtgtxnK7",
      "links": [
        [
          "sea urchin",
          "sea urchin"
        ]
      ]
    }
  ],
  "word": "sea chestnut"
}

{
  "forms": [
    {
      "form": "sea chestnuts",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "sea chestnut (plural sea chestnuts)",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
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        "en:Sea urchins"
      ],
      "glosses": [
        "A sea urchin."
      ],
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          "sea urchin",
          "sea urchin"
        ]
      ]
    }
  ],
  "word": "sea chestnut"
}