"upstack" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "up",
        "3": "stack"
      },
      "expansion": "up- + stack",
      "name": "prefix"
    }
  ],
  "etymology_text": "From up- + stack.",
  "forms": [
    {
      "form": "upstacks",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "upstack (plural upstacks)",
      "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"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms prefixed with up-",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1969, British Ceramic Society, Transactions, Volume 68",
          "text": "Ground particles are fed up the upstack where they circulate to the downstacks and either pass through outlets on the inner radial surfaces (if they are small enough) or are swept again to the bottom of the upstack by low-pressure inlets […]"
        }
      ],
      "glosses": [
        "The upper part of the stack."
      ],
      "id": "en-upstack-en-noun-ulIWNnwx",
      "links": [
        [
          "stack",
          "stack"
        ]
      ]
    }
  ],
  "word": "upstack"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "up",
        "3": "stack"
      },
      "expansion": "up- + stack",
      "name": "prefix"
    }
  ],
  "etymology_text": "From up- + stack.",
  "forms": [
    {
      "form": "upstacks",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "upstack (plural upstacks)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms prefixed with up-",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "1969, British Ceramic Society, Transactions, Volume 68",
          "text": "Ground particles are fed up the upstack where they circulate to the downstacks and either pass through outlets on the inner radial surfaces (if they are small enough) or are swept again to the bottom of the upstack by low-pressure inlets […]"
        }
      ],
      "glosses": [
        "The upper part of the stack."
      ],
      "links": [
        [
          "stack",
          "stack"
        ]
      ]
    }
  ],
  "word": "upstack"
}