BFP relationship
BFP is usually short for "Big Fucking Psomething". But in referring to relationships, it's a play on words for BFF, "Best Friends Forever". BFP is "Best Friends for Pleasure". Similar to FWB "Friends with Benefits" but better friends and better benefits. FWB is usually a temporary situation, where BFP is more permanent. Like someone in an open relationship might have a BFP. They are your go-to people you trust for regularly having group sex.
That 3-way was the most amazing thing ever, so we're upgrading you from our Gym Buddy to a BFP relationship.