"math grenade" meaning in English

{
  "etymology_text": "From its resemblance to a grenade, the weapon.",
  "forms": [
    {
      "form": "math grenades",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "math grenade (plural math grenades)",
      "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"
        }
      ],
      "glosses": [
        "The Curta, a cylindrical hand-held mechanical calculator invented in the 1930s."
      ],
      "id": "en-math_grenade-en-noun-OLTHQE8r",
      "links": [
        [
          "cylindrical",
          "cylindrical"
        ],
        [
          "hand-held",
          "hand-held"
        ],
        [
          "mechanical",
          "mechanical"
        ],
        [
          "calculator",
          "calculator"
        ]
      ],
      "raw_glosses": [
        "(historical, slang) The Curta, a cylindrical hand-held mechanical calculator invented in the 1930s."
      ],
      "synonyms": [
        {
          "word": "pepper mill"
        }
      ],
      "tags": [
        "historical",
        "slang"
      ]
    }
  ],
  "word": "math grenade"
}

{
  "etymology_text": "From its resemblance to a grenade, the weapon.",
  "forms": [
    {
      "form": "math grenades",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "math grenade (plural math grenades)",
      "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",
        "English terms with historical senses"
      ],
      "glosses": [
        "The Curta, a cylindrical hand-held mechanical calculator invented in the 1930s."
      ],
      "links": [
        [
          "cylindrical",
          "cylindrical"
        ],
        [
          "hand-held",
          "hand-held"
        ],
        [
          "mechanical",
          "mechanical"
        ],
        [
          "calculator",
          "calculator"
        ]
      ],
      "raw_glosses": [
        "(historical, slang) The Curta, a cylindrical hand-held mechanical calculator invented in the 1930s."
      ],
      "synonyms": [
        {
          "word": "pepper mill"
        }
      ],
      "tags": [
        "historical",
        "slang"
      ]
    }
  ],
  "word": "math grenade"
}