"trench derby" meaning in English

{
  "forms": [
    {
      "form": "trench derbies",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trench derby (plural trench derbies)",
      "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": "Headwear",
          "orig": "en:Headwear",
          "parents": [
            "Clothing",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "World War I",
          "orig": "en:World War I",
          "parents": [
            "Historical events",
            "History of Europe",
            "War",
            "History",
            "Europe",
            "Conflict",
            "Military",
            "Violence",
            "All topics",
            "Earth",
            "Eurasia",
            "Human behaviour",
            "Society",
            "Fundamental",
            "Nature",
            "Human"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A tin hat."
      ],
      "id": "en-trench_derby-en-noun-7X1fikMA",
      "links": [
        [
          "military",
          "military"
        ],
        [
          "slang",
          "slang"
        ],
        [
          "tin hat",
          "tin hat"
        ]
      ],
      "raw_glosses": [
        "(military slang, World War I) A tin hat."
      ],
      "synonyms": [
        {
          "word": "trench-derby"
        }
      ],
      "tags": [
        "World-War-I",
        "slang"
      ],
      "topics": [
        "government",
        "military",
        "politics",
        "war"
      ]
    }
  ],
  "word": "trench derby"
}

{
  "forms": [
    {
      "form": "trench derbies",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trench derby (plural trench derbies)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English military slang",
        "English multiword terms",
        "English nouns",
        "en:Headwear",
        "en:World War I"
      ],
      "glosses": [
        "A tin hat."
      ],
      "links": [
        [
          "military",
          "military"
        ],
        [
          "slang",
          "slang"
        ],
        [
          "tin hat",
          "tin hat"
        ]
      ],
      "raw_glosses": [
        "(military slang, World War I) A tin hat."
      ],
      "tags": [
        "World-War-I",
        "slang"
      ],
      "topics": [
        "government",
        "military",
        "politics",
        "war"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "trench-derby"
    }
  ],
  "word": "trench derby"
}