"flattest" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "superlative adjective"
      },
      "expansion": "flattest",
      "name": "head"
    }
  ],
  "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"
        },
        {
          "kind": "other",
          "name": "English entries with language name categories using raw markup",
          "parents": [
            "Entries with language name categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1949 March and April, “Maidenhead Bridge”, in Railway Magazine, page 93",
          "text": "Brunel designed a bridge to be constructed in brick, and embodying two of the flattest and largest arches that had ever been constructed; indeed, it would be difficult to find any bridge today of comparable proportions.",
          "type": "quotation"
        }
      ],
      "form_of": [
        {
          "extra": "most flat",
          "word": "flat"
        }
      ],
      "glosses": [
        "superlative form of flat: most flat"
      ],
      "id": "en-flattest-en-adj-jplEEer7",
      "links": [
        [
          "flat",
          "flat#English"
        ]
      ],
      "tags": [
        "form-of",
        "superlative"
      ]
    }
  ],
  "word": "flattest"
}

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "superlative adjective"
      },
      "expansion": "flattest",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "English 2-syllable words",
        "English entries with incorrect language header",
        "English entries with language name categories using raw markup",
        "English non-lemma forms",
        "English superlative adjectives",
        "English terms with quotations"
      ],
      "examples": [
        {
          "ref": "1949 March and April, “Maidenhead Bridge”, in Railway Magazine, page 93",
          "text": "Brunel designed a bridge to be constructed in brick, and embodying two of the flattest and largest arches that had ever been constructed; indeed, it would be difficult to find any bridge today of comparable proportions.",
          "type": "quotation"
        }
      ],
      "form_of": [
        {
          "extra": "most flat",
          "word": "flat"
        }
      ],
      "glosses": [
        "superlative form of flat: most flat"
      ],
      "links": [
        [
          "flat",
          "flat#English"
        ]
      ],
      "tags": [
        "form-of",
        "superlative"
      ]
    }
  ],
  "word": "flattest"
}