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

Services available will include free I-Pass sticker tags to replace plastic transponders, account services for people who use the tollway, and an I-Pass education and enrollment program for income-qualifying Illinois residents, social media information said. —Mike Danahey, Chicago Tribune, 13 Jan. 2026

Frequent travelers can sign up for MacPass and obtain a transponder for their windshield. —Jalen Williams, Freep.com, 9 Jan. 2026

The ship recently activated its transponder, allowing open-source maritime tracking websites to locate the ship as being in the North Atlantic Ocean close to Iceland and the United Kingdom. —Luis Martinez, ABC News, 7 Jan. 2026

Minutes after the pilot’s last transmission to Kuala Lumpur, the plane’s location-tracking transponder stopped broadcasting. —Peter Guo, NBC news, 30 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