"-өөсэй" meaning in Mongolian

{
  "forms": [
    {
      "form": "-öösej",
      "tags": [
        "romanization"
      ]
    }
  ],
  "hyphenation": [
    "өө‧сэй"
  ],
  "lang": "Mongolian",
  "lang_code": "mn",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Mongolian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Mongolian terms with redundant script codes",
          "parents": [
            "Terms with redundant script codes",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "rounded front vowel harmonic form of -аасай (-aasaj)"
      ],
      "id": "en--өөсэй-mn-suffix-FfXDpBZL",
      "links": [
        [
          "-аасай",
          "-аасай#Mongolian"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈɵːsei̯/"
    }
  ],
  "word": "-өөсэй"
}

{
  "forms": [
    {
      "form": "-öösej",
      "tags": [
        "romanization"
      ]
    }
  ],
  "hyphenation": [
    "өө‧сэй"
  ],
  "lang": "Mongolian",
  "lang_code": "mn",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        "Mongolian entries with incorrect language header",
        "Mongolian non-lemma forms",
        "Mongolian suffix forms",
        "Mongolian terms with IPA pronunciation",
        "Mongolian terms with redundant script codes"
      ],
      "glosses": [
        "rounded front vowel harmonic form of -аасай (-aasaj)"
      ],
      "links": [
        [
          "-аасай",
          "-аасай#Mongolian"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈɵːsei̯/"
    }
  ],
  "word": "-өөсэй"
}