"trace horse" meaning in English

{
  "forms": [
    {
      "form": "trace horses",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trace horse (plural trace horses)",
      "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": "Horses",
          "orig": "en:Horses",
          "parents": [
            "Equids",
            "Livestock",
            "Odd-toed ungulates",
            "Agriculture",
            "Animals",
            "Mammals",
            "Applied sciences",
            "Lifeforms",
            "Vertebrates",
            "Sciences",
            "All topics",
            "Life",
            "Chordates",
            "Fundamental",
            "Nature"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "One of the outside horses, in a team of three or more horses that are harnessed side-by-side, drawing a load or vehicle."
      ],
      "id": "en-trace_horse-en-noun-0XjLDWhr",
      "links": [
        [
          "outside",
          "outside"
        ],
        [
          "harness",
          "harness"
        ]
      ],
      "synonyms": [
        {
          "word": "tracehorse"
        },
        {
          "word": "trace-horse"
        }
      ],
      "translations": [
        {
          "code": "grc",
          "lang": "Ancient Greek",
          "roman": "seirāphóros",
          "sense": "outside horse in a team of three or more",
          "tags": [
            "masculine"
          ],
          "word": "σειρᾱφόρος"
        }
      ]
    }
  ],
  "word": "trace horse"
}

{
  "forms": [
    {
      "form": "trace horses",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trace horse (plural trace horses)",
      "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:Horses"
      ],
      "glosses": [
        "One of the outside horses, in a team of three or more horses that are harnessed side-by-side, drawing a load or vehicle."
      ],
      "links": [
        [
          "outside",
          "outside"
        ],
        [
          "harness",
          "harness"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "word": "tracehorse"
    },
    {
      "word": "trace-horse"
    }
  ],
  "translations": [
    {
      "code": "grc",
      "lang": "Ancient Greek",
      "roman": "seirāphóros",
      "sense": "outside horse in a team of three or more",
      "tags": [
        "masculine"
      ],
      "word": "σειρᾱφόρος"
    }
  ],
  "word": "trace horse"
}