"C." meaning in Italian

{
  "head_templates": [
    {
      "args": {
        "1": "it",
        "2": "noun"
      },
      "expansion": "C.",
      "name": "head"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "bass drum",
          "word": "grancassa"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Italian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 4 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "it",
          "name": "Music",
          "orig": "it:Music",
          "parents": [
            "Art",
            "Sound",
            "Culture",
            "Energy",
            "Society",
            "Nature",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Abbreviation of grancassa (“bass drum”)."
      ],
      "id": "en-C.-it-noun-OYwctZi4",
      "links": [
        [
          "music",
          "music"
        ],
        [
          "grancassa",
          "grancassa#Italian"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of grancassa (“bass drum”)."
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "C."
}

{
  "head_templates": [
    {
      "args": {
        "1": "it",
        "2": "noun"
      },
      "expansion": "C.",
      "name": "head"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "bass drum",
          "word": "grancassa"
        }
      ],
      "categories": [
        "Italian abbreviations",
        "Italian entries with incorrect language header",
        "Italian lemmas",
        "Italian nouns",
        "Italian terms spelled with .",
        "Pages with 4 entries",
        "Pages with entries",
        "it:Music"
      ],
      "glosses": [
        "Abbreviation of grancassa (“bass drum”)."
      ],
      "links": [
        [
          "music",
          "music"
        ],
        [
          "grancassa",
          "grancassa#Italian"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of grancassa (“bass drum”)."
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "C."
}