A term used to describe the lax attitude white folk tend to put forth in uncomfortable and awkward social settings. Usually the settings will involve former lovers, spouses, but everyone will try really hard to be positively sugary nice to each other to be polite and overly-friendly.
"Can you believe my ex asked me if I'd like to have dinner with her and her new husband?"
"Damn dude, that's acting white, does she think you're gonna start acting white too?"
"she's definitely acting white..."
a term used with black people to call this person a sell-out. Bascially if you listen to any song not made by a black person, use the word "like" in a sentence more than once, and things even as good as getting good grades.
LaQuesha: so I, like went to the store yesterday and, like, i saw this cute shirt so i, like-
John: LaQuesha! stop acting white!