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

Dolphin : 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

What follows is a wildly chaotic getaway featuring inflatable bubble-ball battles, awkward matchmaking schemes, disastrous sabotage attemptsand even an emergency dolphin CPR situation. —Lily Brown, PEOPLE, 16 June 2026

But the Dolphins still made a 23-game investment into the former Fayetteville State standout. —Omar Kelly, Miami Herald, 16 June 2026

Smith had been with the Dolphins since 2021, spending much of that time on the team’s practice squad but breaking through for a roster spot in 2023. —David Furones, Sun Sentinel, 15 June 2026

Last year, harmful algae blooming off Southern California poisoned hundreds of dolphins and sea lions off Santa Barbara, Ventura, Los Angeles, Orange and San Diego counties, causing strandings along popular beaches. —Paul Rogers, Mercury News, 15 June 2026

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