Definition of bosom friend in English:

bosom friend

noun

informal
  • A very close or intimate friend.

    ‘we have been bosom friends for years’
    • ‘In Carrie, she found a bosom friend and a warm-hearted, though not always quick-witted, companion.’
    • ‘With these two, I felt like bosom friends after twenty minutes.’
    • ‘If she had gone, she would have missed the birthday party of the little girl down the street, of whom she was a bosom friend.’
    • ‘He was my grandfather's bosom friend.’
    • ‘The two, who had been bosom friends since childhood, now fought.’
    • ‘I have absolutely no bosom friends in the club and am only an interested outsider.’
    • ‘He was a bosom friend of their late chairman.’
    • ‘When I saw her whispering something into her bosom-friend's ear, every bit of my good mood was gone again.’
    • ‘He has become a bosom friend of the Prime Minister's since rejoining Labour.’
    • ‘They became bosom friends in the struggle.’