BFF /ˌbiː ef ˈef/ BrE AmE noun [countable] informal
(best friend forever) someone's best friend – used especially by young people, in magazines, and in emails:
It's my BFF's birthday tomorrow.
BFF /ˌbiː ef ˈef/ BrE AmE noun [countable] informal
(best friend forever) someone's best friend – used especially by young people, in magazines, and in emails:
It's my BFF's birthday tomorrow.
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012