"light second" meaning in English

{
  "forms": [
    {
      "form": "light seconds",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "light second (plural light seconds)",
      "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": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Astronomy",
          "orig": "en:Astronomy",
          "parents": [
            "Sciences",
            "Space",
            "All topics",
            "Nature",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Light",
          "orig": "en:Light",
          "parents": [
            "Energy",
            "Nature",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Physics",
          "orig": "en:Physics",
          "parents": [
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Units of measure",
          "orig": "en:Units of measure",
          "parents": [
            "Metrology",
            "Quantity",
            "Applied sciences",
            "Mathematics",
            "Sciences",
            "Formal sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A unit of length equal to the distance light travels in one second: about 300 megameters"
      ],
      "id": "en-light_second-en-noun-tb0r3fpm",
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "physics",
          "physics"
        ],
        [
          "length",
          "length"
        ],
        [
          "distance",
          "distance"
        ],
        [
          "light",
          "light"
        ],
        [
          "second",
          "second"
        ],
        [
          "megameter",
          "megameter"
        ]
      ],
      "raw_glosses": [
        "(astronomy, physics) A unit of length equal to the distance light travels in one second: about 300 megameters"
      ],
      "related": [
        {
          "word": "light year"
        }
      ],
      "topics": [
        "astronomy",
        "natural-sciences",
        "physical-sciences",
        "physics"
      ]
    }
  ],
  "word": "light second"
}

{
  "forms": [
    {
      "form": "light seconds",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "light second (plural light seconds)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "light year"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Astronomy",
        "en:Light",
        "en:Physics",
        "en:Units of measure"
      ],
      "glosses": [
        "A unit of length equal to the distance light travels in one second: about 300 megameters"
      ],
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "physics",
          "physics"
        ],
        [
          "length",
          "length"
        ],
        [
          "distance",
          "distance"
        ],
        [
          "light",
          "light"
        ],
        [
          "second",
          "second"
        ],
        [
          "megameter",
          "megameter"
        ]
      ],
      "raw_glosses": [
        "(astronomy, physics) A unit of length equal to the distance light travels in one second: about 300 megameters"
      ],
      "topics": [
        "astronomy",
        "natural-sciences",
        "physical-sciences",
        "physics"
      ]
    }
  ],
  "word": "light second"
}