: 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
Scientifically known as Otodus megalodon, the Neogene-era shark is estimated to have reached lengths of 50 to 65 feet (15 to 20 meters) and once belonged to a lineage of sharks that evolved during the Cenozoic era, becoming increasingly specialized for preying on and scavenging marine mammals.
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Melissa Cristina Márquez, Forbes, 8 Mar. 2025
In the clip, the mammal could be seen swimming around chunks of ice in the water as the operator of an excavator — who just so happened to be on site — came to its rescue.
—Brenton Blanchet, People.com, 7 Mar. 2025
The marine mammals — which are rarely observed in Thai waters — were seen swimming off Bang Saphan, about 220 miles south of Bangkok, on March 6, according to a Facebook post from the Department of National Parks, Wildlife and Plant Conservation.
—Brendan Rascius, Miami Herald, 7 Mar. 2025
These were the top animal stories on NPR in 2024, including a boy's pregnant octopus
The World Wildlife Fund estimates that plastic pollution kills 100,000 marine mammals each year, either through ingestion or entanglement.
—Rachel Treisman, NPR, 4 Mar. 2025
See All Example Sentences for mammal
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Melissa Cristina Márquez, Forbes, 8 Mar. 2025
In the clip, the mammal could be seen swimming around chunks of ice in the water as the operator of an excavator — who just so happened to be on site — came to its rescue.
—Brenton Blanchet, People.com, 7 Mar. 2025
The marine mammals — which are rarely observed in Thai waters — were seen swimming off Bang Saphan, about 220 miles south of Bangkok, on March 6, according to a Facebook post from the Department of National Parks, Wildlife and Plant Conservation.
—Brendan Rascius, Miami Herald, 7 Mar. 2025
These were the top animal stories on NPR in 2024, including a boy's pregnant octopus
The World Wildlife Fund estimates that plastic pollution kills 100,000 marine mammals each year, either through ingestion or entanglement.
—Rachel Treisman, NPR, 4 Mar. 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 12 Mar. 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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