"down bubble" meaning in English

{
  "etymology_text": "From the bubble of air in the glass tube of the inclinometer, a gauge that indicates the submarine's vertical trim.",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "down bubble (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"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Nautical",
          "orig": "en:Nautical",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1958, Run Silent, Run Deep, 00:01:25",
          "text": "Two degrees down bubble. Hold her at 60.",
          "type": "quotation"
        },
        {
          "ref": "2000, Overdue and Presumed Lost, by Arthur MacMahan, page 181",
          "text": "Dissatisfied with Sailfin's sluggish response, he turned the iron wheel a bit more until the bubble rode backward, indicating that the submarine's stern had lifted relative to the dipping bow. A glance at the calibrations etched into the brass plate behind the liquid-filled glass tubing told him that Sailfin's nose has dipped the required amount. \"We have ten degrees down bubble, sir.\""
        }
      ],
      "glosses": [
        "having a downward trim (of a submarine); usually follows the number of degrees"
      ],
      "id": "en-down_bubble-en-adj-Y3mqPrja",
      "links": [
        [
          "nautical",
          "nautical"
        ],
        [
          "trim",
          "trim"
        ],
        [
          "submarine",
          "submarine"
        ],
        [
          "degree",
          "degree"
        ]
      ],
      "raw_glosses": [
        "(nautical) having a downward trim (of a submarine); usually follows the number of degrees"
      ],
      "related": [
        {
          "word": "up bubble"
        },
        {
          "word": "lose the bubble"
        },
        {
          "word": "angle of attack"
        }
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "nautical",
        "transport"
      ],
      "translations": [
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "s differéntom ná nós",
          "sense": "having a downward trim",
          "tags": [
            "neuter"
          ],
          "word": "с диффере́нтом на́ но́с"
        }
      ]
    }
  ],
  "word": "down bubble"
}

{
  "etymology_text": "From the bubble of air in the glass tube of the inclinometer, a gauge that indicates the submarine's vertical trim.",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "down bubble (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "related": [
    {
      "word": "up bubble"
    },
    {
      "word": "lose the bubble"
    },
    {
      "word": "angle of attack"
    }
  ],
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms with quotations",
        "English uncomparable adjectives",
        "Quotation templates to be cleaned",
        "en:Nautical"
      ],
      "examples": [
        {
          "ref": "1958, Run Silent, Run Deep, 00:01:25",
          "text": "Two degrees down bubble. Hold her at 60.",
          "type": "quotation"
        },
        {
          "ref": "2000, Overdue and Presumed Lost, by Arthur MacMahan, page 181",
          "text": "Dissatisfied with Sailfin's sluggish response, he turned the iron wheel a bit more until the bubble rode backward, indicating that the submarine's stern had lifted relative to the dipping bow. A glance at the calibrations etched into the brass plate behind the liquid-filled glass tubing told him that Sailfin's nose has dipped the required amount. \"We have ten degrees down bubble, sir.\""
        }
      ],
      "glosses": [
        "having a downward trim (of a submarine); usually follows the number of degrees"
      ],
      "links": [
        [
          "nautical",
          "nautical"
        ],
        [
          "trim",
          "trim"
        ],
        [
          "submarine",
          "submarine"
        ],
        [
          "degree",
          "degree"
        ]
      ],
      "raw_glosses": [
        "(nautical) having a downward trim (of a submarine); usually follows the number of degrees"
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "nautical",
        "transport"
      ]
    }
  ],
  "translations": [
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "s differéntom ná nós",
      "sense": "having a downward trim",
      "tags": [
        "neuter"
      ],
      "word": "с диффере́нтом на́ но́с"
    }
  ],
  "word": "down bubble"
}