1. a person who works in or travels through underground tunnels, especially in subway systems
Usage: informal
2. a member of an underground resistance movement or secret organization
Usage: historical

Examples

• The experienced undergrounder knew every tunnel in the subway system.
• She worked as an undergrounder maintaining the electrical systems below the city.
• The old undergrounder shared stories of the resistance during wartime.
• Many undergrounders risked their lives to help people escape during the occupation.
• The undergrounder emerged from the maintenance tunnel covered in dust.
• Local undergrounders warned about flooding in the lower tunnels.