"secunda feria" meaning in Latin

{
  "forms": [
    {
      "form": "secunda fēria",
      "tags": [
        "canonical",
        "feminine"
      ]
    },
    {
      "form": "secundae fēriae",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "secunda<+> fēria<1>"
      },
      "expansion": "secunda fēria f (genitive secundae fēriae); first declension",
      "name": "la-noun"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "Monday",
          "word": "fēria secunda"
        }
      ],
      "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 secunda (“Monday”)"
      ],
      "id": "en-secunda_feria-la-noun-8NvU5h3Z",
      "links": [
        [
          "fēria secunda",
          "feria secunda#Latin"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "declension-1"
      ]
    }
  ],
  "word": "secunda feria"
}

{
  "forms": [
    {
      "form": "secunda fēria",
      "tags": [
        "canonical",
        "feminine"
      ]
    },
    {
      "form": "secundae fēriae",
      "tags": [
        "genitive"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "secunda<+> fēria<1>"
      },
      "expansion": "secunda fēria f (genitive secundae fēriae); first declension",
      "name": "la-noun"
    }
  ],
  "lang": "Latin",
  "lang_code": "la",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "Monday",
          "word": "fēria secunda"
        }
      ],
      "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 secunda (“Monday”)"
      ],
      "links": [
        [
          "fēria secunda",
          "feria secunda#Latin"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "declension-1"
      ]
    }
  ],
  "word": "secunda feria"
}