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

Russian MiG-31 interceptors flew over Estonia for about 12 minutes with transponders – onboard devices that automatically respond to radar signals by transmitting an aircraft’s identity and altitude, enabling air traffic control and air defense systems to track it – switched off. —Frederic Lemieux, Fortune, 19 Feb. 2026

Wednesday, the plane signaled an emergency using its transponder and landed back at Hobby Airport about 17 minutes after taking off. —Alexandra Skores, CNN Money, 18 Feb. 2026

Larger drones are required to carry a radio transponder that identifies the drone’s owner and broadcasts its position to help avert collisions. —ABC News, 13 Feb. 2026

When American star Jordan Stolz attempts to win four individual gold medals in speed skating, data on his runs will be sent back via an Omega transponder worn on his ankle. —Andrew Greif, NBC news, 10 Feb. 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