"plain wrapper" meaning in English

{
  "forms": [
    {
      "form": "plain wrappers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "plain wrapper (plural plain wrappers)",
      "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"
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          "source": "w"
        },
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          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
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      ],
      "glosses": [
        "Synonym of plain brown wrapper (“unmarked police car”)"
      ],
      "id": "en-plain_wrapper-en-noun-iCYGUga8",
      "links": [
        [
          "plain brown wrapper",
          "plain brown wrapper#English"
        ]
      ],
      "qualifier": "CB radio",
      "raw_glosses": [
        "(CB radio, slang) Synonym of plain brown wrapper (“unmarked police car”)"
      ],
      "synonyms": [
        {
          "extra": "unmarked police car",
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "plain brown wrapper"
        }
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "plain wrapper"
}

{
  "forms": [
    {
      "form": "plain wrappers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "plain wrapper (plural plain wrappers)",
      "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 slang",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Synonym of plain brown wrapper (“unmarked police car”)"
      ],
      "links": [
        [
          "plain brown wrapper",
          "plain brown wrapper#English"
        ]
      ],
      "qualifier": "CB radio",
      "raw_glosses": [
        "(CB radio, slang) Synonym of plain brown wrapper (“unmarked police car”)"
      ],
      "synonyms": [
        {
          "extra": "unmarked police car",
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "plain brown wrapper"
        }
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "word": "plain wrapper"
}