"zebra mule" meaning in English

{
  "forms": [
    {
      "form": "zebra mules",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "zebra mule (plural zebra mules)",
      "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": "lifeform",
          "langcode": "en",
          "name": "Equids",
          "orig": "en:Equids",
          "parents": [
            "Odd-toed ungulates",
            "Mammals",
            "Vertebrates",
            "Chordates",
            "Animals",
            "Lifeforms",
            "All topics",
            "Life",
            "Fundamental",
            "Nature"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Synonym of zebrule"
      ],
      "id": "en-zebra_mule-en-noun-qLgWTvh8",
      "links": [
        [
          "zebrule",
          "zebrule#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "zebrule"
        }
      ]
    }
  ],
  "word": "zebra mule"
}

{
  "forms": [
    {
      "form": "zebra mules",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "zebra mule (plural zebra mules)",
      "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",
        "en:Equids"
      ],
      "glosses": [
        "Synonym of zebrule"
      ],
      "links": [
        [
          "zebrule",
          "zebrule#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "zebrule"
        }
      ]
    }
  ],
  "word": "zebra mule"
}