"stack z's" meaning in English

{
  "etymology_text": "See z's. Sleeping cartoon characters are often depicted with a string of z's rising from the nose or mouth.",
  "forms": [
    {
      "form": "stacks z's",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "stacking z's",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "stacked z's",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "stacked z's",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "stack z's (third-person singular simple present stacks z's, present participle stacking z's, simple past and past participle stacked z's)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Sleep",
          "orig": "en:Sleep",
          "parents": [
            "Body",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "To sleep; to be asleep."
      ],
      "id": "en-stack_z's-en-verb-YyyzpMUV",
      "links": [
        [
          "sleep",
          "sleep"
        ],
        [
          "asleep",
          "asleep"
        ]
      ],
      "raw_glosses": [
        "(slang) To sleep; to be asleep."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "LL-Q1860 (eng)-Flame, not lame-stack z's.wav",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/3/39/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/3/39/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav.ogg"
    }
  ],
  "word": "stack z's"
}

{
  "etymology_text": "See z's. Sleeping cartoon characters are often depicted with a string of z's rising from the nose or mouth.",
  "forms": [
    {
      "form": "stacks z's",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "stacking z's",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "stacked z's",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "stacked z's",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "stack z's (third-person singular simple present stacks z's, present participle stacking z's, simple past and past participle stacked z's)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English slang",
        "English verbs",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Sleep"
      ],
      "glosses": [
        "To sleep; to be asleep."
      ],
      "links": [
        [
          "sleep",
          "sleep"
        ],
        [
          "asleep",
          "asleep"
        ]
      ],
      "raw_glosses": [
        "(slang) To sleep; to be asleep."
      ],
      "tags": [
        "slang"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "LL-Q1860 (eng)-Flame, not lame-stack z's.wav",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/3/39/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/3/39/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav/LL-Q1860_%28eng%29-Flame%2C_not_lame-stack_z%26%2339%3Bs.wav.ogg"
    }
  ],
  "word": "stack z's"
}