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

While civilian aircraft are required to keep transponders active, military aircraft may switch them off during sensitive operations, a practice that can increase risks in congested or shared airspace. —Antonio María Delgado, Miami Herald, 15 Dec. 2025

One way transponders do that is by squawking, or sending a code to air traffic control to identify itself and provide information, like altitude. —Mirna Alsharif, NBC news, 15 Dec. 2025

The JetBlue pilot stated the military aircraft did not have its transponder turned on. —Zach Wichter, USA Today, 15 Dec. 2025

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

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