"underbalanced" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "under",
        "3": "balanced"
      },
      "expansion": "under- + balanced",
      "name": "prefix"
    }
  ],
  "etymology_text": "under- + balanced",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "underbalanced (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "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 under-",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Describing a method of drilling for petroleum in which the pressure in the wellbore is kept lower than that of the formation being drilled, thus allowing fluid to enter the well as soon as it is found."
      ],
      "id": "en-underbalanced-en-adj-VSxxxR3a",
      "links": [
        [
          "drilling",
          "drilling"
        ],
        [
          "petroleum",
          "petroleum"
        ],
        [
          "pressure",
          "pressure"
        ],
        [
          "wellbore",
          "wellbore"
        ],
        [
          "formation",
          "formation"
        ]
      ],
      "related": [
        {
          "word": "overbalanced"
        }
      ],
      "tags": [
        "not-comparable"
      ],
      "wikipedia": [
        "underbalanced drilling"
      ]
    }
  ],
  "word": "underbalanced"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "under",
        "3": "balanced"
      },
      "expansion": "under- + balanced",
      "name": "prefix"
    }
  ],
  "etymology_text": "under- + balanced",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "underbalanced (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "related": [
    {
      "word": "overbalanced"
    }
  ],
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English terms prefixed with under-",
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      ],
      "glosses": [
        "Describing a method of drilling for petroleum in which the pressure in the wellbore is kept lower than that of the formation being drilled, thus allowing fluid to enter the well as soon as it is found."
      ],
      "links": [
        [
          "drilling",
          "drilling"
        ],
        [
          "petroleum",
          "petroleum"
        ],
        [
          "pressure",
          "pressure"
        ],
        [
          "wellbore",
          "wellbore"
        ],
        [
          "formation",
          "formation"
        ]
      ],
      "tags": [
        "not-comparable"
      ],
      "wikipedia": [
        "underbalanced drilling"
      ]
    }
  ],
  "word": "underbalanced"
}