: 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
Both viruses are highly contagious and often fatal to mammals, such as dogs and raccoons, according to information from the Cornell College of Veterinary Medicine and the American Veterinary Medical Association.
—
Natalie Neysa Alund, USA Today, 11 Sep. 2025
Lizards, snakes, and the tuatara (collectively known as lepidosaurs) boast over 12,000 species, outnumbering both birds and mammals.
—Mrigakshi Dixit, Interesting Engineering, 10 Sep. 2025
Alongside this, large-scale genetic studies have revealed sweeping changes in the human brain that are not seen in other mammals.
—Lucy Notarantonio, MSNBC Newsweek, 9 Sep. 2025
The majority of these extinctions were among mammals (21 genera) and birds (37 genera), the study noted.
—Katie Hunt, CNN Money, 9 Sep. 2025
See All Example Sentences for mammal
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Natalie Neysa Alund, USA Today, 11 Sep. 2025
Lizards, snakes, and the tuatara (collectively known as lepidosaurs) boast over 12,000 species, outnumbering both birds and mammals.
—Mrigakshi Dixit, Interesting Engineering, 10 Sep. 2025
Alongside this, large-scale genetic studies have revealed sweeping changes in the human brain that are not seen in other mammals.
—Lucy Notarantonio, MSNBC Newsweek, 9 Sep. 2025
The majority of these extinctions were among mammals (21 genera) and birds (37 genera), the study noted.
—Katie Hunt, CNN Money, 9 Sep. 2025
See All Example Sentences for mammal
Cite this Entry
“Mammal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mammal. Accessed 13 Sep. 2025.
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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