"black cow" meaning in English

{
  "forms": [
    {
      "form": "black cows",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "black cow (plural black cows)",
      "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"
        }
      ],
      "examples": [
        {
          "ref": "1977, Donald Fagen, Walter Becker (lyrics and music), “Black Cow”, in Aja, performed by Steely Dan:",
          "text": "Just when it seems so clear / That it's over now / Drink your big black cow / And get out of here",
          "type": "quote"
        }
      ],
      "glosses": [
        "A root beer float."
      ],
      "id": "en-black_cow-en-noun-j~aIzjor",
      "links": [
        [
          "root beer float",
          "root beer float"
        ]
      ],
      "raw_glosses": [
        "(slang) A root beer float."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "black cow"
}

{
  "forms": [
    {
      "form": "black cows",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "black cow (plural black cows)",
      "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 slang",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "1977, Donald Fagen, Walter Becker (lyrics and music), “Black Cow”, in Aja, performed by Steely Dan:",
          "text": "Just when it seems so clear / That it's over now / Drink your big black cow / And get out of here",
          "type": "quote"
        }
      ],
      "glosses": [
        "A root beer float."
      ],
      "links": [
        [
          "root beer float",
          "root beer float"
        ]
      ],
      "raw_glosses": [
        "(slang) A root beer float."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "black cow"
}