"FRL" meaning in English

{
  "forms": [
    {
      "form": "FRLs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "FRL (plural FRLs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "fixed red light"
        }
      ],
      "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"
        }
      ],
      "glosses": [
        "Initialism of fixed red light."
      ],
      "id": "en-FRL-en-noun-gVNuJ0d4",
      "links": [
        [
          "rail transport",
          "rail transport"
        ],
        [
          "fixed",
          "fixed#English"
        ],
        [
          "red light",
          "red light#English"
        ]
      ],
      "raw_glosses": [
        "(rail transport) Initialism of fixed red light."
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "initialism"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "FRL"
}

{
  "forms": [
    {
      "form": "FRLs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "FRL (plural FRLs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "fixed red light"
        }
      ],
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English initialisms",
        "English lemmas",
        "English nouns",
        "English words without vowels",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Rail transportation"
      ],
      "glosses": [
        "Initialism of fixed red light."
      ],
      "links": [
        [
          "rail transport",
          "rail transport"
        ],
        [
          "fixed",
          "fixed#English"
        ],
        [
          "red light",
          "red light#English"
        ]
      ],
      "raw_glosses": [
        "(rail transport) Initialism of fixed red light."
      ],
      "tags": [
        "abbreviation",
        "alt-of",
        "initialism"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "FRL"
}