OPP Share definition Flag Short for: Other People's Plates. Used in describing someone who only likes to eat what food other people have on their plate or have ordered at a restaurant. Courtney ordered the chicken milanese, but I know she'll just eat off OPP.Alex: You want a bite of my salad?Ashley: Yea, I'm down with OPP! OPP by Cojoface March 18, 2010 Get the OPP mug.