"sü" meaning in Basque

{
  "head_templates": [
    {
      "args": {
        "1": "in"
      },
      "expansion": "sü inan",
      "name": "eu-noun"
    }
  ],
  "lang": "Basque",
  "lang_code": "eu",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "fire",
          "word": "su"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Basque entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 6 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Souletin Basque",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Souletin form of su (“fire”)"
      ],
      "id": "en-sü-eu-noun-aHY2tCvL",
      "links": [
        [
          "su",
          "su#Basque"
        ]
      ],
      "tags": [
        "Souletin",
        "alt-of",
        "inanimate"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/s̺y/",
      "tags": [
        "Souletin"
      ]
    }
  ],
  "word": "sü"
}

{
  "categories": [
    "Pages with 6 entries",
    "Pages with entries"
  ],
  "head_templates": [
    {
      "args": {
        "1": "in"
      },
      "expansion": "sü inan",
      "name": "eu-noun"
    }
  ],
  "lang": "Basque",
  "lang_code": "eu",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "fire",
          "word": "su"
        }
      ],
      "categories": [
        "Basque entries with incorrect language header",
        "Basque inanimate nouns",
        "Basque lemmas",
        "Basque nouns",
        "Basque terms spelled with Ü",
        "Basque terms spelled with ◌̈",
        "Pages with 6 entries",
        "Pages with entries",
        "Souletin Basque"
      ],
      "glosses": [
        "Souletin form of su (“fire”)"
      ],
      "links": [
        [
          "su",
          "su#Basque"
        ]
      ],
      "tags": [
        "Souletin",
        "alt-of",
        "inanimate"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/s̺y/",
      "tags": [
        "Souletin"
      ]
    }
  ],
  "word": "sü"
}