Definition of mammal
: 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
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Merriam-Webster unabridged
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Time Traveler for mammal
The first known use of mammal was in 1811
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