Bosom is a old-fashioned word for the upper breast area.
Other definitions include:
1. the breast of a human being.
2. the breasts of a woman.
3. the part of a garment that covers the breast.
4. the breast, conceived of as the center of feelings or
emotions.
5. something likened to the human breast: the bosom of the
earth.
6. a state of enclosing intimacy; warm closeness: the bosom of
the family.