"desur" meaning in Ancien français

{
  "categories": [
    {
      "kind": "other",
      "name": "Prépositions en ancien français",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Ancien français",
      "orig": "ancien français",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Ancien français",
  "lang_code": "fro",
  "pos": "prep",
  "pos_title": "Préposition",
  "senses": [
    {
      "alt_of": [
        {
          "word": "desor"
        }
      ],
      "glosses": [
        "Variante de desor."
      ],
      "id": "fr-desur-fro-prep-Jos5XMWR",
      "tags": [
        "alt-of"
      ]
    }
  ],
  "word": "desur"
}

{
  "categories": [
    "Prépositions en ancien français",
    "ancien français"
  ],
  "lang": "Ancien français",
  "lang_code": "fro",
  "pos": "prep",
  "pos_title": "Préposition",
  "senses": [
    {
      "alt_of": [
        {
          "word": "desor"
        }
      ],
      "glosses": [
        "Variante de desor."
      ],
      "tags": [
        "alt-of"
      ]
    }
  ],
  "word": "desur"
}