"下穿き" meaning in Japanese

{
  "forms": [
    {
      "form": "下穿き",
      "ruby": [
        [
          "下",
          "した"
        ],
        [
          "穿",
          "ば"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "shitabaki",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "したばき"
      },
      "expansion": "下(した)穿(ば)き • (shitabaki)",
      "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 wikilinks",
          "parents": [
            "Links with redundant wikilinks",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Japanese terms with redundant sortkeys",
          "parents": [
            "Terms with redundant sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "undershorts, underpants"
      ],
      "id": "en-下穿き-ja-noun-zponWbO4",
      "links": [
        [
          "undershorts",
          "undershorts"
        ],
        [
          "underpants",
          "underpants"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ɕita̠ba̠kʲi]"
    }
  ],
  "word": "下穿き"
}

{
  "forms": [
    {
      "form": "下穿き",
      "ruby": [
        [
          "下",
          "した"
        ],
        [
          "穿",
          "ば"
        ]
      ],
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "shitabaki",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "したばき"
      },
      "expansion": "下(した)穿(ば)き • (shitabaki)",
      "name": "ja-noun"
    }
  ],
  "lang": "Japanese",
  "lang_code": "ja",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Japanese entries with incorrect language header",
        "Japanese lemmas",
        "Japanese links with redundant wikilinks",
        "Japanese nouns",
        "Japanese terms spelled with first grade kanji",
        "Japanese terms spelled with jinmeiyō kanji",
        "Japanese terms with IPA pronunciation",
        "Japanese terms with redundant sortkeys",
        "Japanese terms written with two Han script characters"
      ],
      "glosses": [
        "undershorts, underpants"
      ],
      "links": [
        [
          "undershorts",
          "undershorts"
        ],
        [
          "underpants",
          "underpants"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ɕita̠ba̠kʲi]"
    }
  ],
  "word": "下穿き"
}