dolphin

noun

dol·​phin ˈdäl-fən 

ˈdȯl-

1

a

: 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

2

: dolphinfish

3

capitalized : delphinus

4

: a spar or buoy for mooring boats

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 Web

About 30 mammals — including whales, dolphins, dugongs, seals, walruses, otters, and beavers — started on land, before venturing into water even part time. —Paul Smaglik, Discover Magazine, 28 Apr. 2025

The algae has killed sea lions, dolphins and now whales, including a humpback whale and a minke whale, McClatchy News reported. —Helena Wegner, Sacbee.com, 25 Apr. 2025

The post included snaps of the family on the beach and Alba with friends, with additional posts showing Alba visiting waterfalls, going on a cave tour, golfing and swimming with dolphins. —Escher Walcott, People.com, 21 Apr. 2025

Thousands of species can be found there, including coral reefs, sea turtles, whales, dolphins, sharks and manta rays. —Rachel Frazin, The Hill, 18 Apr. 2025

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)

Phrases Containing dolphin

• bottle-nosed dolphin
• bottlenose dolphin
• dolphin striker
• Risso's dolphin
• river dolphin
• spinner dolphin

Kids Definition

dolphin

noun

dol·​phin ˈdäl-fən 

ˈdȯl-

1

a

: any of various small whales with teeth and a long nose

b

: porpoise sense 1

2

: either of two active saltwater food fishes noted for their brilliant coloring