"dog's letter" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "la",
        "3": "littera canīna"
      },
      "expansion": "Calque of Latin littera canīna",
      "name": "clq"
    }
  ],
  "etymology_text": "Calque of Latin littera canīna.",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "dog's letter",
      "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"
        }
      ],
      "examples": [
        {
          "ref": "1640, Samuel Ramsey, The English Language and English Grammar, New York and London: G.P. Putnam's Sons, translation of original by Ben Jonson, published 1892, page 168",
          "text": "R is the Dog's letter, and hurreth in the sound; the tongue striking the inner palate, with a trembling about the teeth.",
          "type": "quotation"
        },
        {
          "ref": "1858, Rosina Bulwer Lytton, The World and His Wife, Or, A Person of Consequence […], volume 2, London: Charles J. Skeet, page 19",
          "text": "And in this short query the dog's letter, the r, whirred through the air, like the ricket of a pheasant rising; […]",
          "type": "quotation"
        }
      ],
      "glosses": [
        "The letter R, which was trilled in Latin, imitating the sound of a snarling dog."
      ],
      "id": "en-dog's_letter-en-noun-xyIX~2Np",
      "links": [
        [
          "R",
          "R"
        ]
      ],
      "raw_glosses": [
        "(rare) The letter R, which was trilled in Latin, imitating the sound of a snarling dog."
      ],
      "tags": [
        "rare"
      ],
      "translations": [
        {
          "code": "la",
          "lang": "Latin",
          "sense": "the letter R",
          "tags": [
            "feminine"
          ],
          "word": "littera canīna"
        }
      ]
    }
  ],
  "word": "dog's letter"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "la",
        "3": "littera canīna"
      },
      "expansion": "Calque of Latin littera canīna",
      "name": "clq"
    }
  ],
  "etymology_text": "Calque of Latin littera canīna.",
  "head_templates": [
    {
      "args": {
        "1": "?"
      },
      "expansion": "dog's letter",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English nouns with unknown or uncertain plurals",
        "English terms calqued from Latin",
        "English terms derived from Latin",
        "English terms with quotations",
        "English terms with rare senses"
      ],
      "examples": [
        {
          "ref": "1640, Samuel Ramsey, The English Language and English Grammar, New York and London: G.P. Putnam's Sons, translation of original by Ben Jonson, published 1892, page 168",
          "text": "R is the Dog's letter, and hurreth in the sound; the tongue striking the inner palate, with a trembling about the teeth.",
          "type": "quotation"
        },
        {
          "ref": "1858, Rosina Bulwer Lytton, The World and His Wife, Or, A Person of Consequence […], volume 2, London: Charles J. Skeet, page 19",
          "text": "And in this short query the dog's letter, the r, whirred through the air, like the ricket of a pheasant rising; […]",
          "type": "quotation"
        }
      ],
      "glosses": [
        "The letter R, which was trilled in Latin, imitating the sound of a snarling dog."
      ],
      "links": [
        [
          "R",
          "R"
        ]
      ],
      "raw_glosses": [
        "(rare) The letter R, which was trilled in Latin, imitating the sound of a snarling dog."
      ],
      "tags": [
        "rare"
      ]
    }
  ],
  "translations": [
    {
      "code": "la",
      "lang": "Latin",
      "sense": "the letter R",
      "tags": [
        "feminine"
      ],
      "word": "littera canīna"
    }
  ],
  "word": "dog's letter"
}