: any of various small marine toothed whales (family Delphinidae) with the snout more or less elongated into a beak and the neck vertebrae partially fused
Note:
While not closely related, dolphins and porpoises share a physical resemblance that often leads to misidentification. Dolphins typically have cone-shaped teeth, curved dorsal fins, and elongated beaks with large mouths, while porpoises have flat, spade-shaped teeth, triangular dorsal fins, and shortened beaks with smaller mouths.
b
: any of several related chiefly freshwater toothed whales (as of the families Platanistidae and Iniidae) : river dolphin
also: a cluster of closely driven piles used as a fender for a dock or as a mooring or guide for boats
Illustration of dolphin
dolphin 1a
Examples of dolphin in a Sentence
Recent Examples on the WebShare [Findings] Veterinarians developed an ultrasound schedule for pregnant dolphins, and marine biologists discovered four new species of walking sharks and found that gray seals clap at each other to communicate underwater.—Rafil Kroll-Zaidi, Harper's Magazine, 8 Nov. 2023 The dolphins are talking (which, of course, Matt Groening already knew…).—Rachel Feltman, Popular Science, 8 Nov. 2023 Bats and dolphins are deservedly famous for their echolocation, but the elephantnose fish has a different superpower sense—electrolocation.—Elizabeth Anne Brown, Scientific American, 6 Nov. 2023 But where the album really gets wild is in experiments that purport to demonstrate dolphins mimicking human speech; their uncanny vocalizations are half cartoonish and half nightmarish.—Philip Sherburne, Pitchfork, 6 Nov. 2023 We have been bombarded by images of animal deaths this year, with whales washing up on East Coast beaches this summer, and reports that earlier this month more than one hundred dolphins died in the Brazilian Amazon, probably because of warming water and drought.—Liza Featherstone, The New Republic, 18 Oct. 2023 One is a guy who can make his hand vibrate incredibly fast, and the other is a girl with a dolphin blowhole on her back.—Jordan Moreau, Variety, 13 Oct. 2023 There were highways of fish swimming up and down the reefs, sharks everywhere and dolphins.—Catrin Einhorn Thea Traff, New York Times, 26 Oct. 2023 The veterans group is open to submarine crew who have qualified to wear the warfare specialty pin, the dolphins (silver or gold).—Linda McIntosh, San Diego Union-Tribune, 20 Oct. 2023 See More
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'dolphin.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Word History
Etymology
Middle English delphyn, dolphyn, from Anglo-French delphin, alteration of Old French dalfin, from Medieval Latin dalfinus, alteration of Latin delphinus, from Greek delphin-, delphis; akin to Greek delphys womb, Sanskrit garbha
First Known Use
14th century, in the meaning defined at sense 1a(1)
Time Traveler
The first known use of dolphin was
in the 14th century
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