: 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
Rock the Ocean Foundation is a conservation nonprofit whose core work protects sea turtles, marine mammals, coral reefs, sharks, and marine habitats.
—
Mankaprr Conteh, Rolling Stone, 16 Oct. 2025
Sunday’s closure of the park that opened in 1955 was celebrated by animal rights activists who had lobbied for decades to free the marine mammals inside.
—Jim Edwards, Fortune, 14 Oct. 2025
The marine mammals now at the Seaquarium will be relocated to new homes, while a marina, restaurants, and a scenic public baywalk will line the edge of Biscayne Bay.
—Milena Malaver, Miami Herald, 13 Oct. 2025
Thinning sea ice will also threaten other seal species, walruses and marine mammals in the region, according to the update.
—Nell Lewis, CNN Money, 10 Oct. 2025
See All Example Sentences for mammal
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Mankaprr Conteh, Rolling Stone, 16 Oct. 2025
Sunday’s closure of the park that opened in 1955 was celebrated by animal rights activists who had lobbied for decades to free the marine mammals inside.
—Jim Edwards, Fortune, 14 Oct. 2025
The marine mammals now at the Seaquarium will be relocated to new homes, while a marina, restaurants, and a scenic public baywalk will line the edge of Biscayne Bay.
—Milena Malaver, Miami Herald, 13 Oct. 2025
Thinning sea ice will also threaten other seal species, walruses and marine mammals in the region, according to the update.
—Nell Lewis, CNN Money, 10 Oct. 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 19 Oct. 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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