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

Ever since Jane Goodall first documented the use of tools by chimps in the 1970s, researchers have observed other species engaging in this sophisticated behavior, including dolphins, elephants, birds and — at a basic level — even some insects. —Jacopo Prisco, CNN Money, 25 Nov. 2025

At 19, she was contracted to work in Thailand at a dolphin attraction facility that had just opened to educate workers, conduct studies on the wild dolphin populations and train the animals. —Kaycee Sloan, Cincinnati Enquirer, 25 Nov. 2025

Dolphin Life, a nonprofit in Key Largo, will take four Seaquarium dolphins that carry the names Ariel, Onyx, Ripley and Zo. —Douglas Hanks, Miami Herald, 24 Nov. 2025

Algal blooms, whose growth is being accelerated by climate change, appear to trigger Alzheimer’s-like brain changes in Florida dolphins, which may be causing them to strand themselves. —Rafil Kroll-Zaidi, Harpers Magazine, 23 Nov. 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