echo

Etymology

From Middle English eccho, ecco, ekko, from Medieval Latin ecco, from Latin echo, from Ancient Greek ἠχώ (ēkhṓ), from ἠχή (ēkhḗ, “sound”). Possibly from the same Proto-Indo-European root as sough.

noun

1. A reflected sound that is heard again by its initial observer.
   Earless ghost swift moths become “invisible” to echolocating bats by forming mating clusters close (less than half a meter) above vegetation and effectively blending into the clutter of echoes that the bat receives from the leaves and stems around them. 2013 May-June, William E. Conner, “An Acoustic Arms Race”, in American Scientist, volume 101, number 3, pages 206–7
2. An utterance repeating what has just been said.
3. (poetry) A device in verse in which a line ends with a word which recalls the sound of the last word of the preceding line.
4. (figurative) Sympathetic recognition; response; answer.
   Many kind, and sincere speeches found an echo in his heart. 1878, Robert Louis Stevenson, Will o' the Mill
5. (computing) The displaying on the command line of the command that has just been executed.
6. (computing) An individual discussion forum using the echomail system.
   When someone asks an off-topic question […] they are usually quickly told to knock it off. You can't ask a question about modems in an echo devoted to local-area networks. 1992, Dial in, page 9
7. (international standards) Alternative letter-case form of Echo from the NATO/ICAO Phonetic Alphabet.
8. (whist, bridge) A signal, played in the same manner as a trump signal, made by a player who holds four or more trumps (or, as played by some, exactly three trumps) and whose partner has led trumps or signalled for trumps.
9. (whist, bridge) A signal showing the number held of a plain suit when a high card in that suit is led by one's partner.
10. An antisemitic punctuation symbol or marking, ((( ))), placed around a name or phrase to indicate the person is Jewish or the entity is controlled by Jewish people.
11. (medicine, colloquial, uncountable) Clipping of echocardiography.
12. (medicine, colloquial, countable) Clipping of echocardiogram.

verb

1. (intransitive) Of a sound or sound waves: to reflect off a surface and return; to reverberate or resound.
2. (intransitive, figurative) Of a rumour, opinion, etc.: to spread or reverberate.
   The sense that it takes outrageous fortune to get inoculated echoes here in the Bay Area, where pharmacies have canceled flu-shot clinics, doctors turn away pleading patients and health officials are reduced to telling panicked callers that they should practice good personal hygiene. 2004-10-29, Marco R. Della Cava, “Vaccine shortage pricks tempers”, in Statesman Journal, volume 152, number 214, Salem, OR, page 2A
3. (transitive) To reflect back (a sound).
   Those peals are echoed by the Trojan throng.
   The wondrous sound / Is echoed on forever. 1827, John Keble, The Christian Year: Christmas Day
4. (transitive, figurative) To repeat (another's speech, opinion, etc.).
   Sid echoed his father's point of view.
   Some poems, echoing the purpose of early poetic treatises on scientific principles, attempt to elucidate the mathematical concepts that underlie prime numbers. Others play with primes’ cultural associations. Still others derive their structure from mathematical patterns involving primes. 2013 July-August, Sarah Glaz, “Ode to Prime Numbers”, in American Scientist, volume 101, number 4
   His views were echoed by The Economist, which feared that the effects of modernisation would be no more than "chromium-plated" inefficiency caused by unimaginative railway management and adverse union reaction. March 8 2023, David Clough, “The long road that led to Beeching”, in RAIL, number 978, page 43
5. (computing, transitive) To repeat its input as input to some other device or system.
   The device that is to echo the characters should be optioned for echoplexing. 1991, Martin D. Seyer, RS-232 made easy
6. (intransitive, whist, bridge) To give the echo signal, informing one's partner about cards one holds.