"volcanic glass" meaning in English

{
  "forms": [
    {
      "form": "volcanic glasses",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~"
      },
      "expansion": "volcanic glass (countable and uncountable, plural volcanic glasses)",
      "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": "topical",
          "langcode": "en",
          "name": "Glass",
          "orig": "en:Glass",
          "parents": [
            "Materials",
            "Manufacturing",
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A natural glass produced by the cooling of molten lava, or a liquid fraction of it, too rapidly to permit crystallization."
      ],
      "id": "en-volcanic_glass-en-noun-A~Ruzcb7",
      "links": [
        [
          "glass",
          "glass"
        ],
        [
          "lava",
          "lava"
        ],
        [
          "crystallization",
          "crystallization"
        ]
      ],
      "tags": [
        "countable",
        "uncountable"
      ],
      "wikipedia": [
        "volcanic glass"
      ]
    }
  ],
  "word": "volcanic glass"
}

{
  "forms": [
    {
      "form": "volcanic glasses",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~"
      },
      "expansion": "volcanic glass (countable and uncountable, plural volcanic glasses)",
      "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 uncountable nouns",
        "en:Glass"
      ],
      "glosses": [
        "A natural glass produced by the cooling of molten lava, or a liquid fraction of it, too rapidly to permit crystallization."
      ],
      "links": [
        [
          "glass",
          "glass"
        ],
        [
          "lava",
          "lava"
        ],
        [
          "crystallization",
          "crystallization"
        ]
      ],
      "tags": [
        "countable",
        "uncountable"
      ],
      "wikipedia": [
        "volcanic glass"
      ]
    }
  ],
  "word": "volcanic glass"
}