"苦土" meaning in Japanese

{
  "forms": [
    {
      "form": "苦土",
      "ruby": [
        [
          "苦",
          "く"
        ],
        [
          "土",
          "ど"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "kudo",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "くど"
      },
      "expansion": "苦(く)土(ど) • (kudo)",
      "name": "ja-noun"
    }
  ],
  "lang": "Japanese",
  "lang_code": "ja",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Japanese entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese links with redundant alt parameters",
          "parents": [
            "Links with redundant alt parameters",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese links with redundant wikilinks",
          "parents": [
            "Links with redundant wikilinks",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with 2 kanji",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with redundant sortkeys",
          "parents": [
            "Terms with redundant sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 2 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "ja",
          "name": "Inorganic compounds",
          "orig": "ja:Inorganic compounds",
          "parents": [
            "Matter",
            "Chemistry",
            "Nature",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "ja",
          "name": "Minerals",
          "orig": "ja:Minerals",
          "parents": [
            "Matter",
            "Mineralogy",
            "Chemistry",
            "Nature",
            "Geology",
            "Sciences",
            "All topics",
            "Earth sciences",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "derived": [
        {
          "english": "magnesia lime",
          "roman": "kudosekkai",
          "ruby": [
            [
              "苦土石灰",
              "くどせっかい"
            ]
          ],
          "word": "苦土石灰"
        },
        {
          "roman": "kudoso",
          "ruby": [
            [
              "苦土素",
              "くどそ"
            ]
          ],
          "word": "苦土素: magnesium"
        },
        {
          "roman": "ryōkudoseki",
          "ruby": [
            [
              "菱苦土石",
              "りょうくどせき"
            ]
          ],
          "word": "菱苦土石: magnesite"
        }
      ],
      "glosses": [
        "magnesia, magnesium oxide"
      ],
      "id": "en-苦土-ja-noun-HckDKv0q",
      "links": [
        [
          "magnesia",
          "magnesia"
        ],
        [
          "magnesium oxide",
          "magnesium oxide"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "other": "くど"
    },
    {
      "ipa": "[kɯ̟do̞]"
    }
  ],
  "word": "苦土"
}

{
  "derived": [
    {
      "english": "magnesia lime",
      "roman": "kudosekkai",
      "ruby": [
        [
          "苦土石灰",
          "くどせっかい"
        ]
      ],
      "word": "苦土石灰"
    },
    {
      "roman": "kudoso",
      "ruby": [
        [
          "苦土素",
          "くどそ"
        ]
      ],
      "word": "苦土素: magnesium"
    },
    {
      "roman": "ryōkudoseki",
      "ruby": [
        [
          "菱苦土石",
          "りょうくどせき"
        ]
      ],
      "word": "菱苦土石: magnesite"
    }
  ],
  "forms": [
    {
      "form": "苦土",
      "ruby": [
        [
          "苦",
          "く"
        ],
        [
          "土",
          "ど"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "kudo",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "くど"
      },
      "expansion": "苦(く)土(ど) • (kudo)",
      "name": "ja-noun"
    }
  ],
  "lang": "Japanese",
  "lang_code": "ja",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Japanese entries with incorrect language header",
        "Japanese lemmas",
        "Japanese links with redundant alt parameters",
        "Japanese links with redundant wikilinks",
        "Japanese nouns",
        "Japanese terms spelled with first grade kanji",
        "Japanese terms spelled with third grade kanji",
        "Japanese terms with 2 kanji",
        "Japanese terms with IPA pronunciation",
        "Japanese terms with non-redundant non-automated sortkeys",
        "Japanese terms with redundant sortkeys",
        "Pages with 2 entries",
        "Pages with entries",
        "ja:Inorganic compounds",
        "ja:Minerals"
      ],
      "glosses": [
        "magnesia, magnesium oxide"
      ],
      "links": [
        [
          "magnesia",
          "magnesia"
        ],
        [
          "magnesium oxide",
          "magnesium oxide"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "other": "くど"
    },
    {
      "ipa": "[kɯ̟do̞]"
    }
  ],
  "word": "苦土"
}

{
  "called_from": "parser/1336",
  "msg": "no corresponding start tag found for </span>",
  "path": [
    "苦土"
  ],
  "section": "Japanese",
  "subsection": "noun",
  "title": "苦土",
  "trace": ""
}