mammals Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. any of a large class of warmblooded usually hairy vertebrates whose offspring are fed with milk secreted by the female mammary glands Example Sentence All mammals have hair. Synonyms cow; elephant; cat Antonyms reptile Hear It! Say It! Write It! mammals Switch to cursive Start Share with your friends: