1 a a person's breast or chest, esp. a woman's. b colloq. each of a woman's breasts. c the enclosure formed by a person's breast and arms.
2 an emotional centre, esp. as the source of an enfolding relationship (in the bosom of one's family).
3 the part of a woman's dress covering the breast.
Phrases and idioms:
bosom friend a very close or intimate friend.
Etymology: OE bosm f. Gmc
Useful english dictionary. 2012.