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

As of September 14, IFAW has been involved in 100 dolphin and porpoise strandings in Cape Cod and southeastern Massachusetts in 2025. —Margherita Bassi, Popular Science, 25 Sep. 2025

The trip included lectures on grizzlies, a walking tour to learn how to recognize bear tracks, kayaking and a high-speed boat trip to see orcas and dolphins. —Judy Bart Kancigor, Oc Register, 25 Sep. 2025

The International Whaling Commission reports that approximately 34 species of whales and dolphins have been observed in Costa Rica, including two distinct humpback whale populations. —Raven Brunner, PEOPLE, 23 Sep. 2025

From open ocean shallows where dolphins surf the waves to quiet estuaries perfect for teaching calves to hunt, Folly offers an ideal year-round playground. —Alexandra Emanuelli, Southern Living, 18 Sep. 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