breast

n.

1. The forepart of the body above the abdomen

   chest, thorax, heart, bosom; see chest 2.

2. A protuberant mammary gland

   bosom, mammary gland, teat, mammilla, nipple, bust, dug (especially of animals), udder (especially of cows), tit*, titty*, jug*, boobie*, boob*, knocker*. *

3. One's inner self

   mind, heart, bosom, thoughts, conscience, soul, feelings, psyche, spirit, essential nature, being, character, innermost being, heart of hearts, core; see also mind 1, soul 2.

breast refers to the front part of the human torso from the shoulders to the abdomen, or designates either of the female mammary glands; bosom refers to the entire human breast or to a woman's two breasts but, except in euphemistic applications a big-bosomed matron, is now more common in figurative usage, where it implies the human breast as a source of feeling, a protective, loving enclosure, etc. the bosom of his family; bust, as considered here, almost always implies the female breasts and is the conventional term in referring to silhouette, form, etc., as in garment fitting or beauty contests

beat one's breast

make a clean breast of