"seat back" meaning in English

{
  "forms": [
    {
      "form": "seat backs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "seat back (plural seat backs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "seatback"
        }
      ],
      "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"
        }
      ],
      "examples": [
        {
          "ref": "2023 July 26, Pip Dunn, “Merseyrail '777s' are OK for passengers”, in RAIL, number 988, page 59:",
          "text": "There is an 18×27cm headrest, which at its lowest is incorporated some 5cm into the seat back.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative form of seatback."
      ],
      "id": "en-seat_back-en-noun-AoIzzjMc",
      "links": [
        [
          "seatback",
          "seatback#English"
        ]
      ],
      "related": [
        {
          "word": "back seat"
        },
        {
          "word": "sit back"
        }
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "seat back"
}

{
  "forms": [
    {
      "form": "seat backs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "seat back (plural seat backs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "back seat"
    },
    {
      "word": "sit back"
    }
  ],
  "senses": [
    {
      "alt_of": [
        {
          "word": "seatback"
        }
      ],
      "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"
      ],
      "examples": [
        {
          "ref": "2023 July 26, Pip Dunn, “Merseyrail '777s' are OK for passengers”, in RAIL, number 988, page 59:",
          "text": "There is an 18×27cm headrest, which at its lowest is incorporated some 5cm into the seat back.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative form of seatback."
      ],
      "links": [
        [
          "seatback",
          "seatback#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "seat back"
}