"master cylinder" meaning in English

{
  "forms": [
    {
      "form": "master cylinders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "master cylinder (plural master cylinders)",
      "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"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Engineering",
          "orig": "en:Engineering",
          "parents": [
            "Applied sciences",
            "Technology",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A control device that converts nonhydraulic pressure into hydraulic pressure."
      ],
      "id": "en-master_cylinder-en-noun-gPJJeHPB",
      "links": [
        [
          "engineering",
          "engineering#Noun"
        ],
        [
          "control",
          "control#English"
        ],
        [
          "device",
          "device#English"
        ],
        [
          "nonhydraulic",
          "nonhydraulic#English"
        ],
        [
          "pressure",
          "pressure#English"
        ],
        [
          "hydraulic",
          "hydraulic#English"
        ]
      ],
      "raw_glosses": [
        "(engineering) A control device that converts nonhydraulic pressure into hydraulic pressure."
      ],
      "related": [
        {
          "word": "slave cylinder"
        }
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "physical-sciences"
      ],
      "translations": [
        {
          "code": "fr",
          "lang": "French",
          "sense": "control device",
          "tags": [
            "masculine"
          ],
          "word": "maître-cylindre"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "osnovnój cilíndr",
          "sense": "control device",
          "tags": [
            "masculine"
          ],
          "word": "основно́й цили́ндр"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "glávnyj cilíndr",
          "sense": "control device",
          "tags": [
            "masculine"
          ],
          "word": "гла́вный цили́ндр"
        }
      ],
      "wikipedia": [
        "master cylinder"
      ]
    }
  ],
  "word": "master cylinder"
}

{
  "forms": [
    {
      "form": "master cylinders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "master cylinder (plural master cylinders)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "slave cylinder"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Engineering"
      ],
      "glosses": [
        "A control device that converts nonhydraulic pressure into hydraulic pressure."
      ],
      "links": [
        [
          "engineering",
          "engineering#Noun"
        ],
        [
          "control",
          "control#English"
        ],
        [
          "device",
          "device#English"
        ],
        [
          "nonhydraulic",
          "nonhydraulic#English"
        ],
        [
          "pressure",
          "pressure#English"
        ],
        [
          "hydraulic",
          "hydraulic#English"
        ]
      ],
      "raw_glosses": [
        "(engineering) A control device that converts nonhydraulic pressure into hydraulic pressure."
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "physical-sciences"
      ],
      "wikipedia": [
        "master cylinder"
      ]
    }
  ],
  "translations": [
    {
      "code": "fr",
      "lang": "French",
      "sense": "control device",
      "tags": [
        "masculine"
      ],
      "word": "maître-cylindre"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "osnovnój cilíndr",
      "sense": "control device",
      "tags": [
        "masculine"
      ],
      "word": "основно́й цили́ндр"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "glávnyj cilíndr",
      "sense": "control device",
      "tags": [
        "masculine"
      ],
      "word": "гла́вный цили́ндр"
    }
  ],
  "word": "master cylinder"
}