bosom
ˈbʊzəm noun
1 the front part of a woman’s chest [书面] 〔女人的〕胸部 C usually singular 一般用单数 | written
2 a woman’s breast 〔女人的〕乳房 C usually plural 一般用复数
5
bosom friend/buddy/pal
a very close friend [文] 密友,知己,心腹之交 literary