"Fuck you and your mother". Generally used as a sign of irritation or being unhappy. Especially used when some idiot has just said something very stupid to you.
Johnny: "Game's at 6:00 tonight."
Danny: "Hey Lisa, you know the game's at 6:00 right?"
Lisa: "Do I look stupid to you?! FYAYM!"
the letters “fyaym” which means fuck you and yo mama
Ray: you so stupid fuck you
Aaliyah:fyaym stupid bitch