"combination boiler" meaning in English

{
  "forms": [
    {
      "form": "combination boilers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "combination boiler (plural combination boilers)",
      "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": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": "combi boiler"
        }
      ],
      "glosses": [
        "A boiler that can provide domestic hot water as well as central heating."
      ],
      "id": "en-combination_boiler-en-noun-EPqZPKM0",
      "links": [
        [
          "boiler",
          "boiler"
        ],
        [
          "domestic hot water",
          "domestic hot water"
        ],
        [
          "central heating",
          "central heating"
        ]
      ]
    }
  ],
  "word": "combination boiler"
}

{
  "derived": [
    {
      "word": "combi boiler"
    }
  ],
  "forms": [
    {
      "form": "combination boilers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "combination boiler (plural combination boilers)",
      "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",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Translation table header lacks gloss"
      ],
      "glosses": [
        "A boiler that can provide domestic hot water as well as central heating."
      ],
      "links": [
        [
          "boiler",
          "boiler"
        ],
        [
          "domestic hot water",
          "domestic hot water"
        ],
        [
          "central heating",
          "central heating"
        ]
      ]
    }
  ],
  "word": "combination boiler"
}