bosom buddy

plural bosom buddies

1. informalA very close friend.

   Although they were far from bosom buddies, she liked Mary Jackson as much as anyone on the street.

   1996, Stephen King, The Regulators, Penguin, →ISBN

   2 more examples

   He made a telephone call to his bosom buddy, drinking companion and confidant, CBS Sports Director Bill MacPhail.

   1967 January 13, Paul O'Neil, “Super Bowl's Superman”, in Life, retrieved 23 Nov 2010, page 78

   Campaigning together frequently this fall, the former rivals became, if not bosom buddies, closer than either ever expected.

   2004 November 15, Matthew Cooper, “2004 Election: Candidates In the Wings”, in Time

   Synonyms: bosom friend, cater-cousin, intimate