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

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

The proposal’s pilot program does entertain transponders and odometer photography, neither of which is ideal from privacy or administrative efficiency perspectives, respectively. —Andrew Leahey, Forbes.com, 22 June 2025

Although the Black Hawk had a transponder to appear on radar, ADS-B is significantly more accurate. —Greg Wehner, Fox News, 7 Feb. 2025

Juno’s radio transponder, which communicates with Earth, sending and receiving signals. —Robin Andrews, Wired News, 15 June 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