"x-" meaning in Portuguese

{
  "head_templates": [
    {
      "args": {
        "1": "pt",
        "2": "prefix"
      },
      "expansion": "x-",
      "name": "head"
    }
  ],
  "lang": "Portuguese",
  "lang_code": "pt",
  "pos": "prefix",
  "senses": [
    {
      "alt_of": [
        {
          "word": "X-"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 3 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Portuguese entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "pt",
          "name": "Sandwiches",
          "orig": "pt:Sandwiches",
          "parents": [
            "Foods",
            "Eating",
            "Food and drink",
            "Human behaviour",
            "All topics",
            "Human",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Alternative spelling of X-"
      ],
      "id": "en-x--pt-prefix-8OHLuiMg",
      "links": [
        [
          "X-",
          "X-#Portuguese"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ʃis/",
      "tags": [
        "Brazil"
      ]
    },
    {
      "ipa": "/ʃis/",
      "tags": [
        "Brazil"
      ]
    },
    {
      "ipa": "/ʃiʃ/",
      "tags": [
        "Rio-de-Janeiro"
      ]
    },
    {
      "ipa": "/ʃiʃ/",
      "tags": [
        "Portugal"
      ]
    }
  ],
  "word": "x-"
}

{
  "head_templates": [
    {
      "args": {
        "1": "pt",
        "2": "prefix"
      },
      "expansion": "x-",
      "name": "head"
    }
  ],
  "lang": "Portuguese",
  "lang_code": "pt",
  "pos": "prefix",
  "senses": [
    {
      "alt_of": [
        {
          "word": "X-"
        }
      ],
      "categories": [
        "Pages with 3 entries",
        "Pages with entries",
        "Portuguese 1-syllable words",
        "Portuguese entries with incorrect language header",
        "Portuguese lemmas",
        "Portuguese prefixes",
        "Portuguese terms with IPA pronunciation",
        "pt:Sandwiches"
      ],
      "glosses": [
        "Alternative spelling of X-"
      ],
      "links": [
        [
          "X-",
          "X-#Portuguese"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ʃis/",
      "tags": [
        "Brazil"
      ]
    },
    {
      "ipa": "/ʃis/",
      "tags": [
        "Brazil"
      ]
    },
    {
      "ipa": "/ʃiʃ/",
      "tags": [
        "Rio-de-Janeiro"
      ]
    },
    {
      "ipa": "/ʃiʃ/",
      "tags": [
        "Portugal"
      ]
    }
  ],
  "word": "x-"
}