FAV stands for "forever a virgin". This is the type of term that you would label someone who is unlikely or never (in you or your friends opinion) going to receive the "action" that every human being covets. Often used to describe someone who is unknowingly making a fool out of themselves.
After finishing up his drink at the bar, Matthew couldn't help notice a FAV on stage doing disco moves in his pink skinny jeans.
Yeah, he's my Fav With Benefits. He's going to come over later so we can have some FWB time. He's always generous and helps me with reaching orgasm. I return the favor then he comes back a few days later and the cycle continues.
A "Fav Eva" is a person you cannot stand, they are typically annoying, extremely full of themselves and overall your worst enemy, but they do not know this, only you know this, because one always pretends to a be the "Fav Eva's" best friend, they will secretly despise them while being completely two-faced and pretending they love them...a VERY sarcastic term.
Jared: Hi Taylor! What you doing tonight?!?
Taylor: AH hey Jared! I'm not quite sure how about you?
Jared: Don't know yet...hit me up though I wanna see your face tonight.
Taylor: Oh I'll definitely give you a call!
(Jared leaves)
Taylor: Ew, just saw a fav eva.
Maddi: Who?!
Taylor: Jared..he told me to "hit him up"...what a fav eva.