: any of a class (Mammalia) of warm-blooded higher vertebrates (such as placentals, marsupials, or monotremes) that nourish their young with milk secreted by mammary glands, have the skin usually more or less covered with hair, and include humans
mammal-like
adjective
or less commonly mammallike
mammal-like behavior
mammallike reptiles
Examples of mammal in a Sentence
Human beings, dogs, and cats are all mammals.
Recent Examples on the Web
Life only became intelligent with the rise of large-brained mammals, like us and our direct ancestors.
—
Big Think, 17 Feb. 2026
The creature was one of Australia’s rarest mammals — a northern hairy-nosed wombat, one of only 400 left in the world, the conservancy said.
—Hanna Wickes, Miami Herald, 13 Feb. 2026
The Indiana Department of Natural Resources began a series of reintroduction efforts in the 1990s, and over the past three decades, Hoosiers have spotted the small semi-aquatic mammals in almost every corner of Indiana and elsewhere in Marion County.
—Sophie Hartley, IndyStar, 11 Feb. 2026
Their eggs, laid in open wounds or on mucous membranes, would then not hatch into the flesh-eating maggots that can infest livestock, wild mammals, household pets and even humans.
—John Hanna, Fortune, 10 Feb. 2026
See All Example Sentences for mammal
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Big Think, 17 Feb. 2026
The creature was one of Australia’s rarest mammals — a northern hairy-nosed wombat, one of only 400 left in the world, the conservancy said.
—Hanna Wickes, Miami Herald, 13 Feb. 2026
The Indiana Department of Natural Resources began a series of reintroduction efforts in the 1990s, and over the past three decades, Hoosiers have spotted the small semi-aquatic mammals in almost every corner of Indiana and elsewhere in Marion County.
—Sophie Hartley, IndyStar, 11 Feb. 2026
Their eggs, laid in open wounds or on mucous membranes, would then not hatch into the flesh-eating maggots that can infest livestock, wild mammals, household pets and even humans.
—John Hanna, Fortune, 10 Feb. 2026
See All Example Sentences for mammal
Cite this Entry
“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 19 Feb. 2026.
Copy CitationKids Definition
mammal
noun
mam·mal
ˈmam-əl 
: any of a class of warm-blooded vertebrates that include human beings and all other animals that nourish their young with milk produced by mammary glands and have the skin usually more or less covered with hair
Medical Definition
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