"海千山千" meaning in 日本語

{
  "categories": [
    {
      "kind": "other",
      "name": "日本語",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "日本語 成句",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "海に千年、山に千年生きた蛇は竜になるとの言い伝えより。"
  ],
  "lang": "日本語",
  "lang_code": "ja",
  "pos": "phrase",
  "pos_title": "成句",
  "senses": [
    {
      "glosses": [
        "世の中の裏も表も知り尽くした経験豊富でずる賢こい人物のこと。"
      ],
      "id": "ja-海千山千-ja-phrase-pbSQMTHD",
      "ruby": [
        [
          "裏",
          "うら"
        ],
        [
          "表",
          "おもて"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "word": "海千河千"
    },
    {
      "word": "山千海千"
    }
  ],
  "tags": [
    "idiomatic"
  ],
  "translations": [
    {
      "lang": "英語",
      "lang_code": "en",
      "word": "warhorse"
    }
  ],
  "word": "海千山千"
}

{
  "categories": [
    "日本語",
    "日本語 成句"
  ],
  "etymology_texts": [
    "海に千年、山に千年生きた蛇は竜になるとの言い伝えより。"
  ],
  "lang": "日本語",
  "lang_code": "ja",
  "pos": "phrase",
  "pos_title": "成句",
  "senses": [
    {
      "glosses": [
        "世の中の裏も表も知り尽くした経験豊富でずる賢こい人物のこと。"
      ],
      "ruby": [
        [
          "裏",
          "うら"
        ],
        [
          "表",
          "おもて"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "word": "海千河千"
    },
    {
      "word": "山千海千"
    }
  ],
  "tags": [
    "idiomatic"
  ],
  "translations": [
    {
      "lang": "英語",
      "lang_code": "en",
      "word": "warhorse"
    }
  ],
  "word": "海千山千"
}