"-" meaning in Greek

{
  "lang": "Greek",
  "lang_code": "el",
  "pos": "character",
  "senses": [
    {
      "alt_of": [
        {
          "word": "Τ"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Greek entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Greek terms in nonstandard scripts",
          "parents": [
            "Terms in nonstandard scripts",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Greek terms with non-redundant manual script codes",
          "parents": [
            "Terms with non-redundant manual script codes",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Visual rendering of Morse code for Τ."
      ],
      "id": "en---el-character-nNUPehPO",
      "links": [
        [
          "Τ",
          "Τ#Translingual"
        ]
      ],
      "tags": [
        "alt-of",
        "letter",
        "morse-code",
        "visual-rendering"
      ]
    }
  ],
  "word": "-"
}

{
  "lang": "Greek",
  "lang_code": "el",
  "pos": "character",
  "senses": [
    {
      "alt_of": [
        {
          "word": "Τ"
        }
      ],
      "categories": [
        "Greek entries with incorrect language header",
        "Greek lemmas",
        "Greek letters",
        "Greek terms in nonstandard scripts",
        "Greek terms with non-redundant manual script codes"
      ],
      "glosses": [
        "Visual rendering of Morse code for Τ."
      ],
      "links": [
        [
          "Τ",
          "Τ#Translingual"
        ]
      ],
      "tags": [
        "alt-of",
        "letter",
        "morse-code",
        "visual-rendering"
      ]
    }
  ],
  "word": "-"
}