"mystery ship" meaning in English

{
  "forms": [
    {
      "form": "mystery ships",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mystery ship (plural mystery ships)",
      "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",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "One of the secret British Q-ships, also known as \"decoy vessels\" or \"special service ships\", which served as submarine decoy vessels during World War I."
      ],
      "id": "en-mystery_ship-en-noun-YJsukOO6",
      "links": [
        [
          "Q-ship",
          "Q-ship"
        ],
        [
          "submarine",
          "submarine"
        ],
        [
          "decoy",
          "decoy"
        ],
        [
          "vessels",
          "vessels"
        ],
        [
          "World War I",
          "World War I"
        ]
      ],
      "qualifier": "boats",
      "raw_glosses": [
        "(dated, boats) One of the secret British Q-ships, also known as \"decoy vessels\" or \"special service ships\", which served as submarine decoy vessels during World War I."
      ],
      "tags": [
        "dated"
      ]
    }
  ],
  "word": "mystery ship"
}

{
  "forms": [
    {
      "form": "mystery ships",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mystery ship (plural mystery ships)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English dated terms",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "One of the secret British Q-ships, also known as \"decoy vessels\" or \"special service ships\", which served as submarine decoy vessels during World War I."
      ],
      "links": [
        [
          "Q-ship",
          "Q-ship"
        ],
        [
          "submarine",
          "submarine"
        ],
        [
          "decoy",
          "decoy"
        ],
        [
          "vessels",
          "vessels"
        ],
        [
          "World War I",
          "World War I"
        ]
      ],
      "qualifier": "boats",
      "raw_glosses": [
        "(dated, boats) One of the secret British Q-ships, also known as \"decoy vessels\" or \"special service ships\", which served as submarine decoy vessels during World War I."
      ],
      "tags": [
        "dated"
      ]
    }
  ],
  "word": "mystery ship"
}