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 website tracks only vessels with active transponders, meaning additional ships may have crossed with their signals switched off. — Khaled Wassef, CBS News, 29 June 2026

Other ships have likely switched off their transponders to quietly slip through the waterway undetected. — Jason Ma, Fortune, 28 June 2026

Vessel traffic through the strait has picked up dramatically in recent days, with 70 crossings on Wednesday, according to Kpler, which tracks activity using transponder and satellite data. — David Goldman, CNN Money, 26 June 2026

The warning came after a key naval information group had proposed alternative shipping corridors on Saturday, asking shipowners to consider transiting the strait along the southern route with their transponder signals on. — Anniek Bao, CNBC, 25 June 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