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 personal cars could use a toll transponder to pay a fee or just to be counted. —Brad Templeton, Forbes.com, 26 Aug. 2025

Trips taken by the Bensons were listed on the statement by the serial numbers on their E-ZPass transponders. —Mark Pazniokas, Hartford Courant, 18 Aug. 2025

But on the 405 Express Lanes, a driver must have a switchable transponder, moving the dial to tell the system how many are in the vehicle. —Jim Radcliffe, Oc Register, 1 Aug. 2025

On July 16, a U.S. Air Force C-17 transport aircraft flew from Kirtland Air Force Base in New Mexico—home to a significant nuclear weapons depot—to RAF Lakenheath in England with its transponder switched on, making its location publicly visible. —Amanda Castro hannah Parry, MSNBC Newsweek, 29 July 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