"mackerel snapper" meaning in English

{
  "etymology_text": "From the Roman Catholic practice of avoiding meat except fish on Fridays.",
  "forms": [
    {
      "form": "mackerel snappers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mackerel snapper (plural mackerel snappers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Roman Catholicism",
          "orig": "en:Roman Catholicism",
          "parents": [
            "Catholicism",
            "Christianity",
            "Abrahamism",
            "Religion",
            "Culture",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A Roman Catholic."
      ],
      "id": "en-mackerel_snapper-en-noun-PyL~EI2z",
      "links": [
        [
          "derogatory",
          "derogatory"
        ],
        [
          "Roman Catholic",
          "Roman Catholic"
        ]
      ],
      "raw_glosses": [
        "(dated, derogatory, slang) A Roman Catholic."
      ],
      "tags": [
        "dated",
        "derogatory",
        "slang"
      ]
    }
  ],
  "word": "mackerel snapper"
}

{
  "etymology_text": "From the Roman Catholic practice of avoiding meat except fish on Fridays.",
  "forms": [
    {
      "form": "mackerel snappers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mackerel snapper (plural mackerel snappers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English dated terms",
        "English derogatory terms",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English slang",
        "en:Roman Catholicism"
      ],
      "glosses": [
        "A Roman Catholic."
      ],
      "links": [
        [
          "derogatory",
          "derogatory"
        ],
        [
          "Roman Catholic",
          "Roman Catholic"
        ]
      ],
      "raw_glosses": [
        "(dated, derogatory, slang) A Roman Catholic."
      ],
      "tags": [
        "dated",
        "derogatory",
        "slang"
      ]
    }
  ],
  "word": "mackerel snapper"
}