transponder

noun

tran·​spon·​der tran(t)-ˈspän-dər 

: a radio or radar set that upon receiving a designated signal emits a radio signal of its own and that is used especially for the detection, identification, and location of objects and in satellites for relaying communications signals

Did you know?

This word was coined during World War II by simply joining pieces of the words transmitter and responder. Transponders are basic to modern aviation and communications satellites, and they're finding new uses in fields such as medicine as well. But they're now also part of everyday life. The "E-ZPass" that lets you drive right through turnpike tollbooths is a transponder, and the car you're driving may not even start unless it recognizes the signal from your personal key's transponder. In a big crowded foot race, you may carry a tiny transponder on your shoe that records when you cross both the starting line and the finish line.

Examples of transponder in a Sentence

Recent Examples on the Web

During a press conference on Tuesday, March 24, NTSB Chair Jennifer Homendy confirmed that the Port Authority Aircraft Rescue and Firefighting vehicle, which carried two employees in the cab, did not have a transponder. —Natalie Neysa Alund, USA Today, 25 Mar. 2026

Still, the transponders would have allowed controllers in the tower to see them on their instruments, Homendy said. —Thomas Tracy, New York Daily News, 25 Mar. 2026

One concern Homendy raised is that the fire truck and other emergency vehicles at LaGuardia lack transponders that would provide more precise information to the system that controllers rely upon. —ABC News, 25 Mar. 2026

Homendy also said the truck did not have a transponder that would have alerted the control tower of its location. —Jeff Capellini, CBS News, 24 Mar. 2026

Word History

Etymology

transmitter + responder

First Known Use

circa 1944, in the meaning defined above

Rhymes for transponder

• responder
• condor
• fonder
• launder
• mandir
• maunder
• ponder
• squander
• wander
• yonder