"marker light" meaning in English

{
  "forms": [
    {
      "form": "marker lights",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "marker light (plural marker lights)",
      "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": "Rail transportation",
          "orig": "en:Rail transportation",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1954 January, H. P. White, “Vignettes of the Rail”, in Railway Magazine, page 54, at Harmon station, New York:",
          "text": "No sooner had a waiting locomotive backed on to its train, the vociferous 4-6-4 or 4-8-4 re-emerged from under the bridge, and the two red marker lights on the last vehicles passed, than the headlight of the electric engine hauling the following train could be seen under the bridge and the waiting queue of locomotives had moved up one.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A light marking the end of a train."
      ],
      "id": "en-marker_light-en-noun-t7xJmQO7",
      "links": [
        [
          "rail transport",
          "rail transport"
        ],
        [
          "mark",
          "mark"
        ],
        [
          "train",
          "train"
        ]
      ],
      "raw_glosses": [
        "(rail transport) A light marking the end of a train."
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "marker light"
}

{
  "forms": [
    {
      "form": "marker lights",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "marker light (plural marker lights)",
      "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 terms with quotations",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Rail transportation"
      ],
      "examples": [
        {
          "ref": "1954 January, H. P. White, “Vignettes of the Rail”, in Railway Magazine, page 54, at Harmon station, New York:",
          "text": "No sooner had a waiting locomotive backed on to its train, the vociferous 4-6-4 or 4-8-4 re-emerged from under the bridge, and the two red marker lights on the last vehicles passed, than the headlight of the electric engine hauling the following train could be seen under the bridge and the waiting queue of locomotives had moved up one.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A light marking the end of a train."
      ],
      "links": [
        [
          "rail transport",
          "rail transport"
        ],
        [
          "mark",
          "mark"
        ],
        [
          "train",
          "train"
        ]
      ],
      "raw_glosses": [
        "(rail transport) A light marking the end of a train."
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "marker light"
}