cetacean

American  

[si-tey-shuhn] / sɪˈteɪ ʃən /

adjective

1. belonging to the Cetacea, an order of aquatic, chiefly marine mammals, including the whales and dolphins.

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noun

1. a cetacean mammal.

cetacean British  

/ sɪˈteɪʃən /

adjective

1. of, relating to, or belonging to the Cetacea, an order of aquatic placental mammals having no hind limbs and a blowhole for breathing: includes toothed whales (dolphins, porpoises, etc) and whalebone whales (rorquals, right whales, etc)

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noun

1. a whale

cetacean Scientific  

/ sĭ-tā′shən /

1. Any of various, often very large aquatic mammals of the order Cetacea, having a hairless body that resembles that of a fish. Cetaceans have an elongated skull, a flat, horizontal tail, forelimbs modified into broad flippers, and no hind limbs. They breathe through blowholes located usually at the top of the skull. Whales, dolphins, and porpoises are cetaceans.

2. See more at baleen whale toothed whale

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Other Word Forms

• cetaceous adjective

Etymology

Origin of cetacean

1830–40; < New Latin Cetace ( a ) name of the order ( cet-, -acea ) + -an

Explanation

A cetacean is a member of the family of large aquatic mammals such as whales, dolphins, and porpoises. They have tails rather than hind limbs, and they have flippers instead of forearms. The word cetacean comes from the Latin word cetus, which was used to refer to any large sea creature, and the Greek word ketos, which was a sea monster or whale. The suffix acea means "of the nature of," so cetacean describes a creature belonging to the family of whales or dolphins. As an adjective, the word is used to describe things related to this group. If you like whales and dolphins, you may enjoy cetacean stories like "Moby Dick."

Example Sentences

Both are clearly different from the only cetacean circovirus previously known, beaked whale circovirus, which was identified earlier in a stranded whale from the Pacific Ocean.

From Science Daily • Jan. 6, 2026

The drawings inject suspense even into Melville’s encyclopedic chapters on cetacean anatomy.

From The Wall Street Journal • Jan. 2, 2026

They confirmed for the first time that a potentially deadly whale virus, known as cetacean morbillivirus, is circulating above the Arctic Circle.

From BBC • Dec. 18, 2025

Whale populations have dramatically rebounded since the 1986 global moratorium on whaling, despite the many hazards that remain for cetacean species.

From Salon • Aug. 23, 2024

New songs appear on the cetacean hit parade.

From "Cosmos" by Carl Sagan