"split second" meaning in English

{
  "forms": [
    {
      "form": "split seconds",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "split second (plural split seconds)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "split-second"
        }
      ],
      "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"
        }
      ],
      "examples": [
        {
          "ref": "1912, G[ilbert] K[eith] Chesterton, “The Eye of Death; or, The Murder Charge”, in Manalive, New York, N.Y.: John Lane, →OCLC, part II (The Explanations of Innocent Smith), page 182:",
          "text": "It's very dangerous, though, when a man thinks for a split second that he understands death.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative form of split-second"
      ],
      "id": "en-split_second-en-noun-ntpPDXzN",
      "links": [
        [
          "split-second",
          "split-second#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "split second"
}

{
  "forms": [
    {
      "form": "split seconds",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "split second (plural split seconds)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "split-second"
        }
      ],
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "1912, G[ilbert] K[eith] Chesterton, “The Eye of Death; or, The Murder Charge”, in Manalive, New York, N.Y.: John Lane, →OCLC, part II (The Explanations of Innocent Smith), page 182:",
          "text": "It's very dangerous, though, when a man thinks for a split second that he understands death.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative form of split-second"
      ],
      "links": [
        [
          "split-second",
          "split-second#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "split second"
}