"tertia feria" meaning in Latin

{
  "forms": [
    {
      "form": "tertia fēria",
      "tags": [
        "canonical",
        "feminine"
      ]
    },
    {
      "form": "tertiae fēriae",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "tertia<+> fēria<1>"
      },
      "expansion": "tertia fēria f (genitive tertiae fēriae); first declension",
      "name": "la-noun"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "Tuesday",
          "word": "fēria tertia"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "Latin entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Latin feminine nouns in the first declension",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Alternative form of fēria tertia (“Tuesday”)"
      ],
      "id": "en-tertia_feria-la-noun-cyyJRC7I",
      "links": [
        [
          "fēria tertia",
          "feria tertia#Latin"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "declension-1"
      ]
    }
  ],
  "word": "tertia feria"
}

{
  "forms": [
    {
      "form": "tertia fēria",
      "tags": [
        "canonical",
        "feminine"
      ]
    },
    {
      "form": "tertiae fēriae",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "tertia<+> fēria<1>"
      },
      "expansion": "tertia fēria f (genitive tertiae fēriae); first declension",
      "name": "la-noun"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "Tuesday",
          "word": "fēria tertia"
        }
      ],
      "categories": [
        "Latin entries with incorrect language header",
        "Latin feminine nouns",
        "Latin feminine nouns in the first declension",
        "Latin first declension nouns",
        "Latin lemmas",
        "Latin multiword terms",
        "Latin nouns",
        "Latin nouns with red links in their inflection tables",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Alternative form of fēria tertia (“Tuesday”)"
      ],
      "links": [
        [
          "fēria tertia",
          "feria tertia#Latin"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "declension-1"
      ]
    }
  ],
  "word": "tertia feria"
}