"попусту" meaning in Russian

{
  "etymology_templates": [
    {
      "args": {
        "1": "ru",
        "2": "по",
        "3": "пустой",
        "alt2": "пу́сту"
      },
      "expansion": "по (po) + пу́сту (pústu)",
      "name": "af"
    },
    {
      "args": {
        "1": "ru",
        "2": "пусто́й",
        "3": "",
        "4": "futile"
      },
      "expansion": "пусто́й (pustój, “futile”)",
      "name": "m"
    }
  ],
  "etymology_text": "From по (po) + пу́сту (pústu), old short dative of пусто́й (pustój, “futile”).",
  "forms": [
    {
      "form": "по́пусту",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "pópustu",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "по́пусту"
      },
      "expansion": "по́пусту • (pópustu)",
      "name": "ru-adv"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adv",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Russian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "in vain, uselessly"
      ],
      "id": "en-попусту-ru-adv-0LcmdEf~",
      "links": [
        [
          "in vain",
          "in vain"
        ],
        [
          "uselessly",
          "uselessly"
        ]
      ],
      "raw_glosses": [
        "(colloquial) in vain, uselessly"
      ],
      "related": [
        {
          "roman": "po",
          "word": "по"
        },
        {
          "roman": "pustój",
          "word": "пусто́й"
        },
        {
          "roman": "pústo",
          "word": "пу́сто"
        },
        {
          "roman": "pustotá",
          "word": "пустота́"
        },
        {
          "roman": "pustják",
          "word": "пустя́к"
        },
        {
          "roman": "pustétʹ",
          "tags": [
            "imperfective"
          ],
          "word": "пусте́ть"
        },
        {
          "roman": "opustétʹ",
          "tags": [
            "perfective"
          ],
          "word": "опусте́ть"
        },
        {
          "roman": "pústošʹ",
          "word": "пу́стошь"
        },
        {
          "roman": "pustýnja",
          "word": "пусты́ня"
        },
        {
          "roman": "pustýnnyj",
          "word": "пусты́нный"
        },
        {
          "roman": "pustýnnik",
          "word": "пусты́нник"
        },
        {
          "roman": "pústynʹ",
          "word": "пу́стынь"
        }
      ],
      "synonyms": [
        {
          "word": "напра́сно"
        },
        {
          "word": "бесполе́зно"
        },
        {
          "word": "зря"
        }
      ],
      "tags": [
        "colloquial"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ˈpopʊstʊ]"
    }
  ],
  "word": "попусту"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "ru",
        "2": "по",
        "3": "пустой",
        "alt2": "пу́сту"
      },
      "expansion": "по (po) + пу́сту (pústu)",
      "name": "af"
    },
    {
      "args": {
        "1": "ru",
        "2": "пусто́й",
        "3": "",
        "4": "futile"
      },
      "expansion": "пусто́й (pustój, “futile”)",
      "name": "m"
    }
  ],
  "etymology_text": "From по (po) + пу́сту (pústu), old short dative of пусто́й (pustój, “futile”).",
  "forms": [
    {
      "form": "по́пусту",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "pópustu",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "по́пусту"
      },
      "expansion": "по́пусту • (pópustu)",
      "name": "ru-adv"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adv",
  "related": [
    {
      "roman": "po",
      "word": "по"
    },
    {
      "roman": "pustój",
      "word": "пусто́й"
    },
    {
      "roman": "pústo",
      "word": "пу́сто"
    },
    {
      "roman": "pustotá",
      "word": "пустота́"
    },
    {
      "roman": "pustják",
      "word": "пустя́к"
    },
    {
      "roman": "pustétʹ",
      "tags": [
        "imperfective"
      ],
      "word": "пусте́ть"
    },
    {
      "roman": "opustétʹ",
      "tags": [
        "perfective"
      ],
      "word": "опусте́ть"
    },
    {
      "roman": "pústošʹ",
      "word": "пу́стошь"
    },
    {
      "roman": "pustýnja",
      "word": "пусты́ня"
    },
    {
      "roman": "pustýnnyj",
      "word": "пусты́нный"
    },
    {
      "roman": "pustýnnik",
      "word": "пусты́нник"
    },
    {
      "roman": "pústynʹ",
      "word": "пу́стынь"
    }
  ],
  "senses": [
    {
      "categories": [
        "Russian 3-syllable words",
        "Russian adverbs",
        "Russian colloquialisms",
        "Russian compound terms",
        "Russian entries with incorrect language header",
        "Russian lemmas",
        "Russian terms with IPA pronunciation"
      ],
      "glosses": [
        "in vain, uselessly"
      ],
      "links": [
        [
          "in vain",
          "in vain"
        ],
        [
          "uselessly",
          "uselessly"
        ]
      ],
      "raw_glosses": [
        "(colloquial) in vain, uselessly"
      ],
      "synonyms": [
        {
          "word": "напра́сно"
        },
        {
          "word": "бесполе́зно"
        },
        {
          "word": "зря"
        }
      ],
      "tags": [
        "colloquial"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ˈpopʊstʊ]"
    }
  ],
  "word": "попусту"
}