"64mo" meaning in English

{
  "forms": [
    {
      "form": "64mos",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "-",
        "2": "s"
      },
      "expansion": "64mo (usually uncountable, plural 64mos)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Book sizes",
          "orig": "en:Book sizes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Four",
          "orig": "en:Four",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Paper sizes",
          "orig": "en:Paper sizes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Printing",
          "orig": "en:Printing",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Sixty",
          "orig": "en:Sixty",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              212,
              216
            ]
          ],
          "ref": "2000 April 29, Acorn Books, “FS: 2nd Miscellany of 25 NEW ARRIVALS, Sat., April 29, 2000.”, in rec.arts.books.marketplace (Usenet):",
          "text": "39. Reed, C. A., H. F. Harvey, & R. I. Brasher. WESTERN BIRD GUIDE: Birds of the Rockies & West to the Pacific. 286 pgs with index. Color prints throughout. Red fabricoid, with chipped cardboard slipcase. Oblong 64mo. NY: Doubleday, Doran, 1937. Very good condition, with fair case. $21.50 [115273]",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A size of paper or book: 1.87\"-2.5\" x 2.5\"-3.125\"."
      ],
      "id": "en-64mo-en-noun-V6-hH2UZ",
      "links": [
        [
          "printing",
          "printing#Noun"
        ]
      ],
      "qualifier": "paper",
      "raw_glosses": [
        "(paper, printing) A size of paper or book: 1.87\"-2.5\" x 2.5\"-3.125\"."
      ],
      "tags": [
        "uncountable",
        "usually"
      ],
      "topics": [
        "media",
        "printing",
        "publishing"
      ]
    }
  ],
  "word": "64mo"
}

{
  "forms": [
    {
      "form": "64mos",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "-",
        "2": "s"
      },
      "expansion": "64mo (usually uncountable, plural 64mos)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms spelled with numbers",
        "English terms with quotations",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Book sizes",
        "en:Four",
        "en:Paper sizes",
        "en:Printing",
        "en:Sixty"
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              212,
              216
            ]
          ],
          "ref": "2000 April 29, Acorn Books, “FS: 2nd Miscellany of 25 NEW ARRIVALS, Sat., April 29, 2000.”, in rec.arts.books.marketplace (Usenet):",
          "text": "39. Reed, C. A., H. F. Harvey, & R. I. Brasher. WESTERN BIRD GUIDE: Birds of the Rockies & West to the Pacific. 286 pgs with index. Color prints throughout. Red fabricoid, with chipped cardboard slipcase. Oblong 64mo. NY: Doubleday, Doran, 1937. Very good condition, with fair case. $21.50 [115273]",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A size of paper or book: 1.87\"-2.5\" x 2.5\"-3.125\"."
      ],
      "links": [
        [
          "printing",
          "printing#Noun"
        ]
      ],
      "qualifier": "paper",
      "raw_glosses": [
        "(paper, printing) A size of paper or book: 1.87\"-2.5\" x 2.5\"-3.125\"."
      ],
      "tags": [
        "uncountable",
        "usually"
      ],
      "topics": [
        "media",
        "printing",
        "publishing"
      ]
    }
  ],
  "word": "64mo"
}