"tracer bullet" meaning in English

{
  "forms": [
    {
      "form": "tracer bullets",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "tracer bullet (plural tracer bullets)",
      "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": "topical",
          "langcode": "en",
          "name": "Weapons",
          "orig": "en:Weapons",
          "parents": [
            "Hunting",
            "Military",
            "Tools",
            "Human activity",
            "Society",
            "Technology",
            "Human behaviour",
            "All topics",
            "Human",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "bullets which include a pyrotechnic component, allowing their path through the air to be seen."
      ],
      "id": "en-tracer_bullet-en-noun-BKweZmh3",
      "links": [
        [
          "bullet",
          "bullet"
        ],
        [
          "pyrotechnic",
          "pyrotechnic"
        ]
      ],
      "synonyms": [
        {
          "word": "tracer"
        }
      ],
      "wikipedia": [
        "tracer bullet"
      ]
    }
  ],
  "word": "tracer bullet"
}

{
  "forms": [
    {
      "form": "tracer bullets",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "tracer bullet (plural tracer bullets)",
      "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",
        "en:Weapons"
      ],
      "glosses": [
        "bullets which include a pyrotechnic component, allowing their path through the air to be seen."
      ],
      "links": [
        [
          "bullet",
          "bullet"
        ],
        [
          "pyrotechnic",
          "pyrotechnic"
        ]
      ],
      "synonyms": [
        {
          "word": "tracer"
        }
      ],
      "wikipedia": [
        "tracer bullet"
      ]
    }
  ],
  "word": "tracer bullet"
}