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

The transponders can provide air traffic controllers with more precise information about the vehicles and their locations by constantly sending signals to the control tower. —Bruce Shipkowski, Fortune, 29 Apr. 2026

The transponders allow surface tracking systems to identify a vehicle and accurately plot it on a map displayed in the control tower, as well as sound an alarm if a collision is about to happen. —Alexandra Skores, CNN Money, 29 Apr. 2026

The Chinese oil/chemical tanker, which is part of the shadow fleet of ships used by Russia to transport Russian oil in breach of Western sanctions, switched off its location transponder before exiting the strait. —CBS News, 28 Apr. 2026

In the wake of the crash, NTSB Chairperson Jennifer Homendy said the truck should have had a transponder. —Evan Simko-Bednarski, New York Daily News, 28 Apr. 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