Cetacea

plural noun

Ce·​ta·​cea

sēˈtāshēə

: an order of completely aquatic mostly marine eutherian mammals consisting of the whales, dolphins, porpoises, and related forms, all having a very large head, a tapering body like a fish and nearly devoid of hair, forelimbs like paddles, no hind limbs, a tail ending in a broad horizontal fin, a large brain, a complex stomach of four or more chambers, and two mammae posterior in position

Word History

Etymology

New Latin, from neuter plural of cetaceus cetaceous

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!