Bestfriend in law 

Your bestfriend's husband/wife or girlfriend/boyfriend. So if your bestfriend is cheating then you have 2. Also if your bestfriend has a celebrity crush and says they are married that's also your bestfriend in law.

"Hi bestfriend in law" Said Beyonce

Bestfriend in law by YNW Melly's Bestfriend in law January 12, 2020

Best Friend-In Law

When you become best-friends with someone through marriage.

My best friend married Maya's best friend, so now we are best friend-in law's

Best Friend-In Law by Dangeriam December 9, 2009

best friend in law 

The best friend of your spouse.

My wife's best friend Karisti is my best friend in law.

best friend in law by jd999 September 12, 2009

best-friend-in-law 

when your best friend is dating someone the boyfriend/girlfriend becomes your best-friend-in-law

person Dada ad person Sham are dating and person Sham and person Yaya are best friends,Dada and Yaya are now best-friend-in-law

best-friend-in-law by Millionaire Hippe May 13, 2011

Best friend-in-law 

The odd occurence that when you are going out with someone you inherit their best friend as one of your own good friends. Often occurs more that a girl will become very close to her boyfriends best mate than the other way round.

"You and Johnny are such good friends How do you even know him?"
"Oh Hes Toms best mate so hes my Best friend-in-law"

Best friend-in-law by WooBlackbetty December 9, 2008

Best friend-in-law 

When your best friend gets married to the person of their dreams and you’re also friends with that person. Kinda like usual in-laws but likable.

At the wedding Lewton stood up to give his best friend Fischer and his new best friend-in-law Kyla a congratulatory toast.

Best friend-in-law by KingLouie Daturd August 27, 2018