/ˈmaməl/
Noun, pl. mammals
1. An animal of the class Mammalia, characterized by being warm-blooded, having hair and feeding milk to its young. (wiktionary.org)
2. Any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milk. (wordnetweb.princeton.edu)
3. (Paleontology) A vertebrate with three bones in the inner ear and one in the jaw. (wiktionary.org)
4. Any of the endothermic vertebrates belonging to class Mammalia, which are identifiable by the following characteristics: a neocortex, three middle ear bones, a lower jaw made of a single bone, a hairy body covering, a thoracic diaphragm, a four-chambered heart, and females that are mostly viviparous. (biology-online.org)
5. Warm-blooded vertebrate animals belonging to the class mammalia, including all that possess hair and suckle their young. It includes three major groups: placentals and marsupials, which are vivparous, and monotremes, which are oviparous. (biology-online.org)
6. Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young. (online-medical-dictionary.com)
Word origin: Anglicized form of Modern Latin Mammalia (1773), coined 1758 by Linnaeus for the class of mammals, from neuter plural of Late mammalis “of the breast,” from Latin mamma “breast.”