secondhand friend 

a friend you meet through another friend

Oh, she's a friend of Missy. At first she was a secondhand friend but now we're close!

secondhand friend by DMAK939 May 24, 2011

secondhand friend 

someone who isn’t really you’re friend but is friends with one of you’re friends, so you talk about them as if you’re friends

“Fucking Joel!”
“I didn’t know you were friends with Joel”
“I’m not, by Casey is, so I can it lol”
“So you’re secondhand friends?”
“Yep”

secondhand friend by jjedi January 17, 2019

Second Hand Friend Fist Bump 

The fist bump exchanged by two people with a mutual friend.

I don't know the kid but he's also friends with Alex, so we engaged in a Second Hand Friend Fist Bump.

Second Hand Friend Fist Bump by Mis-hap October 24, 2010