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

Digital broadcast signals emitted from the vessel’s transponder and tracked by analytics company Kpler placed the Skipper near Guyana’s offshore between November and December. —Victoria Beaule, ABC News, 12 Dec. 2025

Frequent travelers can sign up for MacPass and obtain a transponder for their windshield. —Jalen Williams, Freep.com, 11 Dec. 2025

Satellite data indicate the plane remained in the air after its transponder shut down for reasons unknown. —Brian Niemietz, Mercury News, 4 Dec. 2025

Minutes later, the plane's transponder, which broadcasts its location, shut down. —CBS News, 3 Dec. 2025

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