"knuckle joint" meaning in English

{
  "forms": [
    {
      "form": "knuckle joints",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "knuckle joint (plural knuckle joints)",
      "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",
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          "source": "w"
        },
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          "name": "Pages with 1 entry",
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          "source": "w"
        },
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          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Engineering",
          "orig": "en:Engineering",
          "parents": [
            "Applied sciences",
            "Technology",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A joint where the forked end of a connecting rod is joined by a bolt to another piece of the machinery."
      ],
      "id": "en-knuckle_joint-en-noun-pZ1FPlaH",
      "links": [
        [
          "engineering",
          "engineering#Noun"
        ],
        [
          "forked",
          "forked"
        ],
        [
          "end",
          "end"
        ],
        [
          "bolt",
          "bolt"
        ],
        [
          "machinery",
          "machinery"
        ]
      ],
      "raw_glosses": [
        "(engineering) A joint where the forked end of a connecting rod is joined by a bolt to another piece of the machinery."
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "word": "knuckle joint"
}

{
  "forms": [
    {
      "form": "knuckle joints",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "knuckle joint (plural knuckle joints)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
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        "English multiword terms",
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        "en:Engineering"
      ],
      "glosses": [
        "A joint where the forked end of a connecting rod is joined by a bolt to another piece of the machinery."
      ],
      "links": [
        [
          "engineering",
          "engineering#Noun"
        ],
        [
          "forked",
          "forked"
        ],
        [
          "end",
          "end"
        ],
        [
          "bolt",
          "bolt"
        ],
        [
          "machinery",
          "machinery"
        ]
      ],
      "raw_glosses": [
        "(engineering) A joint where the forked end of a connecting rod is joined by a bolt to another piece of the machinery."
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "word": "knuckle joint"
}