​BREAST (a word common to Teutonic languages, of the Ger. Brust, possibly connected with an O. Sax. brustian, to bud), the term properly confined to the external projecting parts of the thorax in females, which contain the mammary glands (for anatomy, and diseases, see Mammary Gland); more generally it is used of the external part of the thorax in animals, including man, lying between the neck and the abdomen.