"red-letter" meaning in All languages combined

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "red-letter (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Particularly significant or positive."
      ],
      "id": "en-red-letter-en-adj-vvA16CoW",
      "links": [
        [
          "significant",
          "significant"
        ],
        [
          "positive",
          "positive"
        ]
      ],
      "related": [
        {
          "word": "Red-Letter Christian"
        },
        {
          "word": "red letter day"
        },
        {
          "word": "rubric"
        }
      ],
      "tags": [
        "not-comparable"
      ]
    }
  ],
  "word": "red-letter"
}

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "red-letter (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "related": [
    {
      "word": "Red-Letter Christian"
    },
    {
      "word": "red letter day"
    },
    {
      "word": "rubric"
    }
  ],
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English uncomparable adjectives"
      ],
      "glosses": [
        "Particularly significant or positive."
      ],
      "links": [
        [
          "significant",
          "significant"
        ],
        [
          "positive",
          "positive"
        ]
      ],
      "tags": [
        "not-comparable"
      ]
    }
  ],
  "word": "red-letter"
}