"Tbn." meaning in English

{
  "forms": [
    {
      "form": "Tbn.",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "Tbn."
      },
      "expansion": "Tbn. (plural Tbn.)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "trombone"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 3 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Music",
          "orig": "en:Music",
          "parents": [
            "Art",
            "Sound",
            "Culture",
            "Energy",
            "Society",
            "Nature",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Abbreviation of trombone."
      ],
      "id": "en-Tbn.-en-noun-S8nYqVmb",
      "links": [
        [
          "music",
          "music"
        ],
        [
          "trombone",
          "trombone#English"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of trombone."
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "Tbn."
}

{
  "forms": [
    {
      "form": "Tbn.",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "Tbn."
      },
      "expansion": "Tbn. (plural Tbn.)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "trombone"
        }
      ],
      "categories": [
        "English abbreviations",
        "English countable nouns",
        "English entries with incorrect language header",
        "English indeclinable nouns",
        "English lemmas",
        "English nouns",
        "English nouns with irregular plurals",
        "English terms spelled with .",
        "English words without vowels",
        "Pages with 3 entries",
        "Pages with entries",
        "en:Music"
      ],
      "glosses": [
        "Abbreviation of trombone."
      ],
      "links": [
        [
          "music",
          "music"
        ],
        [
          "trombone",
          "trombone#English"
        ]
      ],
      "raw_glosses": [
        "(music) Abbreviation of trombone."
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "music"
      ]
    }
  ],
  "word": "Tbn."
}