"down cold" meaning in English

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      "expansion": "down cold",
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  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
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      "categories": [
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          "kind": "other",
          "name": "American English",
          "parents": [],
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      "examples": [
        {
          "text": "they've got it down cold"
        }
      ],
      "glosses": [
        "Mastered perfectly; especially, mastered perfectly through memorization."
      ],
      "id": "en-down_cold-en-phrase-l-sXBXnM",
      "links": [
        [
          "Mastered",
          "master#Verb"
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          "memorization",
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      "raw_glosses": [
        "(US, informal) Mastered perfectly; especially, mastered perfectly through memorization."
      ],
      "tags": [
        "US",
        "informal"
      ]
    }
  ],
  "word": "down cold"
}

{
  "head_templates": [
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      "expansion": "down cold",
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  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
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      ],
      "examples": [
        {
          "text": "they've got it down cold"
        }
      ],
      "glosses": [
        "Mastered perfectly; especially, mastered perfectly through memorization."
      ],
      "links": [
        [
          "Mastered",
          "master#Verb"
        ],
        [
          "memorization",
          "memorization"
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        "(US, informal) Mastered perfectly; especially, mastered perfectly through memorization."
      ],
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        "informal"
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  "word": "down cold"
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