"unbackable favourite" meaning in English

{
  "forms": [
    {
      "form": "unbackable favourites",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "unbackable favourite (plural unbackable favourites)",
      "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": "Betting",
          "orig": "en:Betting",
          "parents": [
            "Gambling",
            "Games",
            "Recreation",
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "At $1.01 (or 1/100 in traditional odds), he was the unbackable favourite to win the race.",
          "type": "example"
        }
      ],
      "glosses": [
        "A contestant or competitor whose odds are so short that it is not considered worthwhile betting on."
      ],
      "id": "en-unbackable_favourite-en-noun-MvyAN7Ts",
      "links": [
        [
          "gambling",
          "gambling#Noun"
        ],
        [
          "contestant",
          "contestant"
        ],
        [
          "competitor",
          "competitor"
        ],
        [
          "odds",
          "odds"
        ],
        [
          "short",
          "short"
        ]
      ],
      "raw_glosses": [
        "(gambling) A contestant or competitor whose odds are so short that it is not considered worthwhile betting on."
      ],
      "topics": [
        "gambling",
        "games"
      ]
    }
  ],
  "word": "unbackable favourite"
}

{
  "forms": [
    {
      "form": "unbackable favourites",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "unbackable favourite (plural unbackable favourites)",
      "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",
        "English terms with usage examples",
        "en:Betting"
      ],
      "examples": [
        {
          "text": "At $1.01 (or 1/100 in traditional odds), he was the unbackable favourite to win the race.",
          "type": "example"
        }
      ],
      "glosses": [
        "A contestant or competitor whose odds are so short that it is not considered worthwhile betting on."
      ],
      "links": [
        [
          "gambling",
          "gambling#Noun"
        ],
        [
          "contestant",
          "contestant"
        ],
        [
          "competitor",
          "competitor"
        ],
        [
          "odds",
          "odds"
        ],
        [
          "short",
          "short"
        ]
      ],
      "raw_glosses": [
        "(gambling) A contestant or competitor whose odds are so short that it is not considered worthwhile betting on."
      ],
      "topics": [
        "gambling",
        "games"
      ]
    }
  ],
  "word": "unbackable favourite"
}