"drop frame" meaning in English

{
  "forms": [
    {
      "form": "drop frames",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "drop frame (plural drop frames)",
      "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": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Bicycle types",
          "orig": "en:Bicycle types",
          "parents": [
            "Cycling",
            "Vehicles",
            "Transport",
            "Machines",
            "All topics",
            "Technology",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1958 May, Avram Davidson, “Or All The Seas With Oysters”, in Galaxy Science Fiction, page 58:",
          "text": "I see they're still making drop-frame bikes,\" he said, \"though, with so many women wearing slacks, I wonder they bother.\"",
          "type": "quote"
        }
      ],
      "glosses": [
        "A bicycle with no top tube."
      ],
      "id": "en-drop_frame-en-noun-Hjx4y9GP",
      "links": [
        [
          "bicycle",
          "bicycle"
        ],
        [
          "top tube",
          "top tube"
        ]
      ]
    }
  ],
  "word": "drop frame"
}

{
  "forms": [
    {
      "form": "drop frames",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "drop frame (plural drop frames)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Bicycle types"
      ],
      "examples": [
        {
          "ref": "1958 May, Avram Davidson, “Or All The Seas With Oysters”, in Galaxy Science Fiction, page 58:",
          "text": "I see they're still making drop-frame bikes,\" he said, \"though, with so many women wearing slacks, I wonder they bother.\"",
          "type": "quote"
        }
      ],
      "glosses": [
        "A bicycle with no top tube."
      ],
      "links": [
        [
          "bicycle",
          "bicycle"
        ],
        [
          "top tube",
          "top tube"
        ]
      ]
    }
  ],
  "word": "drop frame"
}