best friend

From Middle English best frend, best freond, equivalent to best +‎ friend. Compare West Frisian bêste freon (“best friend”), Dutch beste vriend (“best friend”), German bester Freund (“best friend”).

best friend (plural best friends)

1. An especially close and trusted friend.
   • 1994, Penny Vincenzi, Wicked Pleasures‎^[1], →ISBN, page 46:

     I know you and Virginia are on best-friend terms.

   • 2001, Lauren, “To me a best friend is everything”, in Marilyn Kielbasa, Janet Claussen, editors, Listen for a Whisper: Prayers, Poems, and Reflections by Girls‎^[2], →ISBN:

     A best friend is always there for you, even when no one else is.

   • 2004, Kenneth D. George, Keeping Mr. Right‎^[3], →ISBN:

     Being best friends means giving up control and allowing ourselves to become vulnerable.

2. (informal) An object or concept considered very useful or helpful to someone.
   • 2005, Jeff Davidson, The Complete Idiot's Guide to Getting Things Done, Penguin, →ISBN, page 212:

     You might even say, the bigger the problem, the greater your creative potential. The problem you're facing is your best friend because it will help to bring out the best in you.

   • 2006, Christopher Duncan, The Career Programmer: Guerilla Tactics for an Imperfect World, Apress, →ISBN:

     As an entrepreneur, a conservative financial outlook is your best friend. Live to fight another day. Running a business also involves a host of legal issues. Talk to some people you respect and trust, get some recommendations, and hire a good lawyer and accountant.

   • 2010, Art Seamans, I See, Said the Blind Man, AuthorHouse, →ISBN, page 48:

     An instructor informed us that in battle, your rifle is your best friend.

3. Used other than figuratively or idiomatically: see best,‎ friend.

• boon companion
• BFF
• bestie
• bosom friend

• worst enemy

• best friend forever

• best girl
• best man