"subdrainage" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "sub",
        "3": "drainage"
      },
      "expansion": "sub- + drainage",
      "name": "prefix"
    }
  ],
  "etymology_text": "sub- + drainage",
  "forms": [
    {
      "form": "subdrainages",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~"
      },
      "expansion": "subdrainage (countable and uncountable, plural subdrainages)",
      "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"
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          "source": "w"
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        {
          "kind": "other",
          "name": "English terms prefixed with sub-",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "drainage of liquid at a level below ground, contrasted with surface drainage"
      ],
      "id": "en-subdrainage-en-noun-z9pBX3iR",
      "links": [
        [
          "drainage",
          "drainage"
        ],
        [
          "liquid",
          "liquid"
        ],
        [
          "ground",
          "ground"
        ],
        [
          "surface",
          "surface"
        ]
      ],
      "tags": [
        "countable",
        "uncountable"
      ]
    }
  ],
  "word": "subdrainage"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "sub",
        "3": "drainage"
      },
      "expansion": "sub- + drainage",
      "name": "prefix"
    }
  ],
  "etymology_text": "sub- + drainage",
  "forms": [
    {
      "form": "subdrainages",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~"
      },
      "expansion": "subdrainage (countable and uncountable, plural subdrainages)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
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        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms prefixed with sub-",
        "English uncountable nouns"
      ],
      "glosses": [
        "drainage of liquid at a level below ground, contrasted with surface drainage"
      ],
      "links": [
        [
          "drainage",
          "drainage"
        ],
        [
          "liquid",
          "liquid"
        ],
        [
          "ground",
          "ground"
        ],
        [
          "surface",
          "surface"
        ]
      ],
      "tags": [
        "countable",
        "uncountable"
      ]
    }
  ],
  "word": "subdrainage"
}