"fourth-class" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "fourth-class (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "American English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1945 July and August, John Gibbons, “Thirty Years of The Railway Magazine”, in Railway Magazine, page 229",
          "text": "Was it once stated that fourth class carriages no longer existed? But I have travelled fourth class in Jugoslavia and also on the C.F.A.E. in Algeria on the line from Oran to Colomb Bechar.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A former class of mail consisting mostly of heavier printed matter."
      ],
      "id": "en-fourth-class-en-adj-hbXCkwd9",
      "links": [
        [
          "class",
          "class"
        ],
        [
          "mail",
          "mail"
        ]
      ],
      "raw_glosses": [
        "(US) A former class of mail consisting mostly of heavier printed matter."
      ],
      "tags": [
        "US",
        "not-comparable"
      ]
    }
  ],
  "word": "fourth-class"
}

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "fourth-class (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "American English",
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms with quotations",
        "English uncomparable adjectives"
      ],
      "examples": [
        {
          "ref": "1945 July and August, John Gibbons, “Thirty Years of The Railway Magazine”, in Railway Magazine, page 229",
          "text": "Was it once stated that fourth class carriages no longer existed? But I have travelled fourth class in Jugoslavia and also on the C.F.A.E. in Algeria on the line from Oran to Colomb Bechar.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A former class of mail consisting mostly of heavier printed matter."
      ],
      "links": [
        [
          "class",
          "class"
        ],
        [
          "mail",
          "mail"
        ]
      ],
      "raw_glosses": [
        "(US) A former class of mail consisting mostly of heavier printed matter."
      ],
      "tags": [
        "US",
        "not-comparable"
      ]
    }
  ],
  "word": "fourth-class"
}