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

Meanwhile, this past weekend, reports emerged that two American military cargo jets deported people to Africa on flights that appear to have had their transponders turned off, preventing tracking by obscuring their locations from public flight databases and other nearby aircraft. —Larisha Paul, Rolling Stone, 24 Sep. 2025

Those aforementioned items—like the homemade transponders that occasionally work and the bombs that always do—are unambiguously the detritus of war. —Paul A. Thompson, Pitchfork, 24 Sep. 2025

Patel addressed speculation about a nearby aircraft's transponder, clarifying that incomplete flight data—not tampering—caused the apparent signal gap. —Amanda Castro mandy Taheri peter Aitken, MSNBC Newsweek, 21 Sep. 2025

Estonia’s military said the jets had their transponders switched off and did not have flight plans, potentially endangering other aircraft. —Sophie Tanno, CNN Money, 20 Sep. 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