: 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
The parasite typically finds points of entry through the eyes, ears, nose, mouth, or genitals of warm-blooded mammals.
—
Angel Saunders, PEOPLE, 4 June 2026
Collectively, Perreault found, humans occupy as much terrain as all other mammals combined, far more than any one species.
—Cody Cottier, Scientific American, 4 June 2026
While much research on animal communication focuses on large mammals thought to have relatively rich communication systems, such as primates and cetaceans (whales and dolphins), Birch said the judges try to cast a wide zoological net.
—Katie Hunt, CNN Money, 3 June 2026
Similarly, retreating glaciers that form the Greenland Ice Sheet carve new valleys and reshape the physical geography, which will likely bring new challenges for the land mammals.
—Staff Author, Travel + Leisure, 1 June 2026
See All Example Sentences for mammal
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Angel Saunders, PEOPLE, 4 June 2026
Collectively, Perreault found, humans occupy as much terrain as all other mammals combined, far more than any one species.
—Cody Cottier, Scientific American, 4 June 2026
While much research on animal communication focuses on large mammals thought to have relatively rich communication systems, such as primates and cetaceans (whales and dolphins), Birch said the judges try to cast a wide zoological net.
—Katie Hunt, CNN Money, 3 June 2026
Similarly, retreating glaciers that form the Greenland Ice Sheet carve new valleys and reshape the physical geography, which will likely bring new challenges for the land mammals.
—Staff Author, Travel + Leisure, 1 June 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 5 Jun. 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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