Top definition
the day in which you celebrate with your best friends.

most commonly celebrated on the 14th of every month.

created in palmdale

friend-"guess what"
friend2"what"
friend-"i got you something for best friend day!"
friend2-"im so glad i saved you from that fire."
by tillyen March 27, 2008
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2
A day where it is acceptable for your significant other to fuck their "best friend." This person can be anyone of their choice but is often an ex girlfriend or boyfriend. It may be played off as "just hanging out" but when they don't come home that night you know what happened.
I know it's your first day off but I am going to go over to Trevor's for best friend day. Ignore why Matt is texting me.
by damit187 July 29, 2017
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