"knuckle under" meaning in English

{
  "forms": [
    {
      "form": "knuckles under",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knuckling under",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knuckled under",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "knuckled under",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "knuckle under (third-person singular simple present knuckles under, present participle knuckling under, simple past and past participle knuckled under)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English phrasal verbs formed with \"under\"",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Spanish translations",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1907, John Galsworthy, “Acute Attack of—‘Pendycitis’”, in The Country House, London: William Heinemann, →OCLC, part III, page 286:",
          "text": "The man is a ruffian. I won't knuckle under to him!",
          "type": "quote"
        }
      ],
      "glosses": [
        "To cooperate or yield when forced or pressured to do so."
      ],
      "id": "en-knuckle_under-en-verb-QNd8ZXnP",
      "links": [
        [
          "cooperate",
          "cooperate"
        ],
        [
          "yield",
          "yield#Verb"
        ],
        [
          "forced",
          "force#Verb"
        ],
        [
          "pressured",
          "pressure#Verb"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, intransitive) To cooperate or yield when forced or pressured to do so."
      ],
      "synonyms": [
        {
          "word": "fall in line"
        }
      ],
      "tags": [
        "idiomatic",
        "intransitive"
      ],
      "translations": [
        {
          "code": "es",
          "lang": "Spanish",
          "sense": "to cooperate or yield when forced or pressured to do so",
          "word": "doblar el espinazo"
        }
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-knuckle under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/4/43/En-au-knuckle_under.ogg/En-au-knuckle_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/4/43/En-au-knuckle_under.ogg"
    }
  ],
  "word": "knuckle under"
}

{
  "forms": [
    {
      "form": "knuckles under",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "knuckling under",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "knuckled under",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "knuckled under",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "knuckle under (third-person singular simple present knuckles under, present participle knuckling under, simple past and past participle knuckled under)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English idioms",
        "English intransitive verbs",
        "English lemmas",
        "English multiword terms",
        "English phrasal verbs",
        "English phrasal verbs formed with \"under\"",
        "English terms with quotations",
        "English verbs",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Spanish translations"
      ],
      "examples": [
        {
          "ref": "1907, John Galsworthy, “Acute Attack of—‘Pendycitis’”, in The Country House, London: William Heinemann, →OCLC, part III, page 286:",
          "text": "The man is a ruffian. I won't knuckle under to him!",
          "type": "quote"
        }
      ],
      "glosses": [
        "To cooperate or yield when forced or pressured to do so."
      ],
      "links": [
        [
          "cooperate",
          "cooperate"
        ],
        [
          "yield",
          "yield#Verb"
        ],
        [
          "forced",
          "force#Verb"
        ],
        [
          "pressured",
          "pressure#Verb"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, intransitive) To cooperate or yield when forced or pressured to do so."
      ],
      "synonyms": [
        {
          "word": "fall in line"
        }
      ],
      "tags": [
        "idiomatic",
        "intransitive"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-knuckle under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/4/43/En-au-knuckle_under.ogg/En-au-knuckle_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/4/43/En-au-knuckle_under.ogg"
    }
  ],
  "translations": [
    {
      "code": "es",
      "lang": "Spanish",
      "sense": "to cooperate or yield when forced or pressured to do so",
      "word": "doblar el espinazo"
    }
  ],
  "word": "knuckle under"
}