"Tr." meaning in Italian

{
  "forms": [
    {
      "form": "Tre.",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f",
        "2": "Tre."
      },
      "expansion": "Tr. f (plural Tre.)",
      "name": "it-noun"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "trumpet",
          "word": "tromba"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Italian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "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 tromba (“trumpet”)."
      ],
      "id": "en-Tr.-it-noun-jX0k4P7M",
      "links": [
        [
          "music",
          "music"
        ],
        [
          "tromba",
          "tromba#Italian"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of tromba (“trumpet”)."
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "feminine"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "Tr."
}

{
  "forms": [
    {
      "form": "Tre.",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "f",
        "2": "Tre."
      },
      "expansion": "Tr. f (plural Tre.)",
      "name": "it-noun"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "trumpet",
          "word": "tromba"
        }
      ],
      "categories": [
        "Italian abbreviations",
        "Italian countable nouns",
        "Italian entries with incorrect language header",
        "Italian feminine nouns",
        "Italian lemmas",
        "Italian nouns",
        "Italian nouns with red links in their headword lines",
        "Italian terms spelled with .",
        "it:Music"
      ],
      "glosses": [
        "Abbreviation of tromba (“trumpet”)."
      ],
      "links": [
        [
          "music",
          "music"
        ],
        [
          "tromba",
          "tromba#Italian"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of tromba (“trumpet”)."
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "feminine"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "Tr."
}