"цслав." meaning in Russian

{
  "forms": [
    {
      "form": "cslav.",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "indecl": "1"
      },
      "expansion": "цслав. • (cslav.) (indeclinable)",
      "name": "ru-adj"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "(cerkovnoslavjánskij): CS, Church Slavonic",
          "word": "церковнославя́нский"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Russian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "abbreviation of церковнославя́нский (cerkovnoslavjánskij): CS, Church Slavonic"
      ],
      "id": "en-цслав.-ru-adj-PSMNRYHx",
      "links": [
        [
          "церковнославя́нский",
          "церковнославянский#Russian"
        ],
        [
          "CS",
          "CS"
        ],
        [
          "Church Slavonic",
          "Church Slavonic"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "indeclinable"
      ]
    }
  ],
  "word": "цслав."
}

{
  "forms": [
    {
      "form": "cslav.",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "indecl": "1"
      },
      "expansion": "цслав. • (cslav.) (indeclinable)",
      "name": "ru-adj"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "(cerkovnoslavjánskij): CS, Church Slavonic",
          "word": "церковнославя́нский"
        }
      ],
      "categories": [
        "Russian abbreviations",
        "Russian adjectives",
        "Russian entries with incorrect language header",
        "Russian indeclinable adjectives",
        "Russian lemmas",
        "Russian terms spelled with .",
        "Russian terms with redundant head parameter"
      ],
      "glosses": [
        "abbreviation of церковнославя́нский (cerkovnoslavjánskij): CS, Church Slavonic"
      ],
      "links": [
        [
          "церковнославя́нский",
          "церковнославянский#Russian"
        ],
        [
          "CS",
          "CS"
        ],
        [
          "Church Slavonic",
          "Church Slavonic"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "indeclinable"
      ]
    }
  ],
  "word": "цслав."
}