To have cum in the ass of a dark-skinned individual, pulled apart his/her ass cheeks, and licked out the "cream filling". If one is feeling particularly adventurous, one might then push the ass cheeks back together and eat them, whatever the fuck that means.
"So you came in her ass. What happened then?"
"'What happened then?' What the fuck do you mean? I fuckin' Oreoed the shit outta that bitch! Literally!"
As a verb, it means a white person got sandwiched by 2 black people. Used as a sexual word.
As an adjective, it means a black person who acts white and totally forgets their own root. This is an offensive term to black people and shouldn't really be used.
(As a verb) Susan got oreoed last night, she seemed to have fun with them!
(As an adjective) An oreoed man is a true betrayal to his own root.