ce·​ta·​cean si-ˈtā-shən How to pronounce cetacean (audio)
: any of an order (Cetacea) of aquatic mostly marine mammals that includes the whales, dolphins, porpoises, and related forms and that have a torpedo-shaped nearly hairless body, paddle-shaped forelimbs but no hind limbs, one or two nares opening externally at the top of the head, and a horizontally flattened tail used for locomotion
cetacean adjective
cetaceous adjective

Examples of cetacean in a Sentence

Recent Examples on the Web Like all other toothed whales, these little Arctic-dwelling cetaceans have an organ on their foreheads that’s referred to as the melon. Tom Hawking, Popular Science, 2 May 2024 The number of gray whale strandings tends to rise between March and May, when the cetaceans pass by the Bay Area on their way to Alaska, according to the academy. Jason Green, The Mercury News, 1 May 2024 Niagara Falls kept cetaceans and seals from colonizing most of the Great Lakes; however, there is evidence from historical records that harbor seals did inhabit Lake Ontario and Lake Champlain up into the early 1800s but were hunted to extinction there. Smithsonian Magazine, Smithsonian Magazine, 27 Mar. 2024 Many of the doomed cetaceans looked skinny or emaciated, while others looked torn up by orcas. Susanne Rust, Los Angeles Times, 27 Mar. 2024 Because both groups of cetaceans were so diverse, some species likely ventured into river and lake ecosystems, seeking less competition for food. Mindy Weisberger, CNN, 26 Mar. 2024 With so many cetaceans in South Georgia’s waters now, plus more than 80 visits by sightseeing vessels every summer, ship strikes are a risk. Douglas Main, Smithsonian Magazine, 18 Jan. 2024 Whales are cetaceans, as are porpoises and dolphins. Allison Futterman, Discover Magazine, 17 Jan. 2024 Whether in the Pacific, Arctic, or Atlantic oceans, the cetaceans, bears, and marine life are uniquely different in each environment, especially when the Arctic Ocean thaws come spring. Jonny Bierman, Travel + Leisure, 20 Oct. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'cetacean.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


ultimately from Latin cetus whale, from Greek kētos

First Known Use

1840, in the meaning defined above

Time Traveler
The first known use of cetacean was in 1840

Dictionary Entries Near cetacean

Cite this Entry

“Cetacean.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cetacean. Accessed 25 May. 2024.

Kids Definition


ce·​ta·​cean si-ˈtā-shən How to pronounce cetacean (audio)
: any of an order of aquatic mammals (as a whale, dolphin, or porpoise)
cetacean adjective

More from Merriam-Webster on cetacean

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