"flap gate" meaning in English

{
  "forms": [
    {
      "form": "flap gates",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "flap gate (plural flap gates)",
      "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": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
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          "source": "w"
        }
      ],
      "glosses": [
        "A device that allows water to flow in one direction only through a culvert; it is used especially to drain surface water from coastal marshes at low tide"
      ],
      "id": "en-flap_gate-en-noun-5U-B-0sl",
      "links": [
        [
          "water",
          "water"
        ],
        [
          "culvert",
          "culvert"
        ]
      ],
      "synonyms": [
        {
          "word": "flapgate"
        }
      ]
    }
  ],
  "word": "flap gate"
}

{
  "forms": [
    {
      "form": "flap gates",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "flap gate (plural flap gates)",
      "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",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "A device that allows water to flow in one direction only through a culvert; it is used especially to drain surface water from coastal marshes at low tide"
      ],
      "links": [
        [
          "water",
          "water"
        ],
        [
          "culvert",
          "culvert"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "word": "flapgate"
    }
  ],
  "word": "flap gate"
}