"cxu" meaning in Esperanto

{
  "head_templates": [
    {
      "args": {
        "1": "eo",
        "2": "particle",
        "cat2": "interrogative particles"
      },
      "expansion": "cxu",
      "name": "head"
    }
  ],
  "lang": "Esperanto",
  "lang_code": "eo",
  "pos": "particle",
  "senses": [
    {
      "alt_of": [
        {
          "word": "ĉu"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Esperanto entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Esperanto interrogative particles",
          "parents": [
            "Interrogative particles",
            "Interrogative pro-forms",
            "Particles",
            "Pro-forms",
            "Lemmas",
            "Terms by semantic function"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Esperanto particles",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "X-system spelling of ĉu"
      ],
      "id": "en-cxu-eo-particle-PRbaJnJD",
      "links": [
        [
          "ĉu",
          "ĉu#Esperanto"
        ]
      ],
      "tags": [
        "X-system",
        "alt-of"
      ]
    }
  ],
  "word": "cxu"
}

{
  "head_templates": [
    {
      "args": {
        "1": "eo",
        "2": "particle",
        "cat2": "interrogative particles"
      },
      "expansion": "cxu",
      "name": "head"
    }
  ],
  "lang": "Esperanto",
  "lang_code": "eo",
  "pos": "particle",
  "senses": [
    {
      "alt_of": [
        {
          "word": "ĉu"
        }
      ],
      "categories": [
        "Esperanto X-system forms",
        "Esperanto entries with incorrect language header",
        "Esperanto interrogative particles",
        "Esperanto lemmas",
        "Esperanto particles",
        "Esperanto terms spelled with X",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "X-system spelling of ĉu"
      ],
      "links": [
        [
          "ĉu",
          "ĉu#Esperanto"
        ]
      ],
      "tags": [
        "X-system",
        "alt-of"
      ]
    }
  ],
  "word": "cxu"
}