A fork of Rural Dictionary
An intimate friend; a really kindred spirit to whom you can confide your inmost soul. Very hard to find.
1) I'm so glad I met Lin. She is a bosom friend! 2) I never expected to find such a bosom friend, but I'm glad I did.
A very close friend. One that you can share everything with. Made popular by Anne in Anne of Green Gables.
Anne: "Diana Barry is my bosom friend"