Bosom friend 

A very close friend. One that you can share everything with. Made popular by Anne in Anne of Green Gables.

Anne: "Diana Barry is my bosom friend"

Bosom friend by TheRealIndianaJones January 2, 2016

Best Friend 

A person who you can trust. Someone who will be there for you no matter what. Someone who cares about you. A best friend wont talk trash behind your back, wont lie to you or about you.

I love my best friend because i can always trust her to be there for me when i need a shoulder to cry on.

Best Friend by ItsTheRealMe101 January 16, 2017

Friendscort

A completely platonic relationship defined by the act of accompanying another in a dangerous or awkward situation. It is a combination of the words friend and escort. It was originally used by improv actors in St. Louis, Missouri to indicate an intent to traverse Cherokee street without peril.

will you please be a friendscort to my car? There were some wingnuts in the parking lot." or "I'll friendscort you to the Justin Bieber concert so you won't look out of place because there will be another 30 year old guy there.

Friendscort by BorisMcGee August 19, 2010

Friendship Sex 

When friends have sex with each other just purely out of friendship, but nothing more. It commonly causes many problems and/or makes the friendship awkward after.

Peter and Anna had friendship sex last night and now they can't look each other in the eye.

Friendship Sex by Belo April 11, 2008

Let's just be friend's 

A comment mainly said by women but can also be used by men. Meaning the person you are wanting to be in a relationship with is not ready and or doesn't like you in that way. Such as;

You: I like you, please will you be my insert partner
Them: oh sorry I think we should just be friend's

Sometimes it can be ment in a mean way so people often misunderstand the use of this phrase. But it will mostly be used as a way for a person to be let down without trying to hurt their feelings. Because if it's sincere then a person likes you but maybe not in the way you interpreted it. So what it means;

You: I want to go out with you
Them: let's just be friend's

What it actually means:

You: I have emotion
Them: right now is not a good time
Or

Them: I'm sorry I don't like you in that way

Or

Them: we have clashing personalities so I don't think we would work well being together
Or

Them: I love someone else and am waiting for them
Or

Them: Your my friend I don't want to affect our friendship.

Let's just be friend's by NeonDetonation May 20, 2019

friendette 

from friend and -ette (feminine gender suffix (marker) of French provenance).
A female friend.

Any word + -ette states a female.
Friend (common gender) + -ette = friendette (feminine gender).
Dude (male gender) + -ette = dudette (feminine gender).

friendette by Yet Another Daniel Nielsen November 20, 2011

Satellite Friend

The friend that is never really part of the "fam" group of friends. They're never on the inside of any circles and only make their revolutions around the outside of close cliques, even though they're friends with all of them.

"Why weren't you there on Saturday, everyone else was"
"Uh because everyone forgot about me and didn't miss me because I'm just a Satellite Friend"

Satellite Friend by Mortal Beauty January 18, 2016