"knuckle up" meaning in English

{
  "forms": [
    {
      "form": "knuckles up",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knuckling up",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knuckled up",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "knuckled up",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "knuckle up (third-person singular simple present knuckles up, present participle knuckling up, simple past and past participle knuckled up)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "African-American Vernacular English",
          "parents": [],
          "source": "w"
        },
        {
          "_dis": "74 19 6",
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w+disamb"
        },
        {
          "_dis": "73 15 12",
          "kind": "other",
          "name": "English phrasal verbs formed with \"up\"",
          "parents": [],
          "source": "w+disamb"
        },
        {
          "_dis": "74 18 8",
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w+disamb"
        },
        {
          "_dis": "83 9 7",
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w+disamb"
        }
      ],
      "examples": [
        {
          "ref": "2012, Vanessa Miller, Latter Rain:",
          "text": "With a resolve to get his son away from these monsters, Isaac knuckled up and mean-mugged his opponent.",
          "type": "quote"
        },
        {
          "ref": "2012, Pink Maxwell, A Scorpion's Sting, page 209:",
          "text": "Tony stumbled a little and when he found his balance, he knuckled up and sent a jab toward Will's neck.",
          "type": "quote"
        }
      ],
      "glosses": [
        "To clench one's fist(s) as though in preparation for a fight."
      ],
      "id": "en-knuckle_up-en-verb-SP3NGsYS",
      "qualifier": "chiefly African-American Vernacular",
      "raw_glosses": [
        "(informal, chiefly African-American Vernacular) To clench one's fist(s) as though in preparation for a fight."
      ],
      "tags": [
        "informal"
      ]
    },
    {
      "categories": [],
      "glosses": [
        "To approach a problem aggressively."
      ],
      "id": "en-knuckle_up-en-verb-f3vbb5vY",
      "raw_glosses": [
        "(informal, by extension) To approach a problem aggressively."
      ],
      "tags": [
        "broadly",
        "informal"
      ]
    },
    {
      "categories": [],
      "glosses": [
        "To strike or fight."
      ],
      "id": "en-knuckle_up-en-verb-bbm3kASp",
      "links": [
        [
          "strike",
          "strike"
        ],
        [
          "fight",
          "fight"
        ]
      ],
      "raw_glosses": [
        "(slang) To strike or fight."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "knuckle up"
}

{
  "categories": [
    "English entries with incorrect language header",
    "English lemmas",
    "English multiword terms",
    "English phrasal verbs",
    "English phrasal verbs formed with \"up\"",
    "English verbs",
    "Pages with 1 entry",
    "Pages with entries"
  ],
  "forms": [
    {
      "form": "knuckles up",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knuckling up",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knuckled up",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "knuckled up",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "knuckle up (third-person singular simple present knuckles up, present participle knuckling up, simple past and past participle knuckled up)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "African-American Vernacular English",
        "English informal terms",
        "English terms with quotations",
        "Quotation templates to be cleaned"
      ],
      "examples": [
        {
          "ref": "2012, Vanessa Miller, Latter Rain:",
          "text": "With a resolve to get his son away from these monsters, Isaac knuckled up and mean-mugged his opponent.",
          "type": "quote"
        },
        {
          "ref": "2012, Pink Maxwell, A Scorpion's Sting, page 209:",
          "text": "Tony stumbled a little and when he found his balance, he knuckled up and sent a jab toward Will's neck.",
          "type": "quote"
        }
      ],
      "glosses": [
        "To clench one's fist(s) as though in preparation for a fight."
      ],
      "qualifier": "chiefly African-American Vernacular",
      "raw_glosses": [
        "(informal, chiefly African-American Vernacular) To clench one's fist(s) as though in preparation for a fight."
      ],
      "tags": [
        "informal"
      ]
    },
    {
      "categories": [
        "English informal terms"
      ],
      "glosses": [
        "To approach a problem aggressively."
      ],
      "raw_glosses": [
        "(informal, by extension) To approach a problem aggressively."
      ],
      "tags": [
        "broadly",
        "informal"
      ]
    },
    {
      "categories": [
        "English slang"
      ],
      "glosses": [
        "To strike or fight."
      ],
      "links": [
        [
          "strike",
          "strike"
        ],
        [
          "fight",
          "fight"
        ]
      ],
      "raw_glosses": [
        "(slang) To strike or fight."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "knuckle up"
}