1. a person who signals with a flag, especially one who directs traffic or warns of hazards on a road or construction site
2. a person or thing that flags or becomes tired or weak
Usage: informal

Examples

• The flagger stood at the edge of the construction zone, holding a stop sign.
• A flagger directed cars through the roadwork with hand signals.
• The runner was a flagger in the final mile of the marathon.
• Energy levels began to flagger as the day went on.
• The flagger waved the flag to alert drivers of the upcoming hazard.