“In your face” is a recent American idiom. It can have two meanings. The first, and most common, is a form of derision. The second means someone or something is brash, arrogant, or extreme. It also has an even more recent abbreviated off-shoot, “face” or “your face.”
Example of the first: “Ha! I scored! In your face!”
Example of the second: “That new band was in-your-face loud!”
Example of the latter: “I think you’re stupid,” Sue said. “Your face is stupid,” replied Dave.
Where did it come from?
“In your face” was first coined in 1976 in Charles Rosen‘s novel about basketball – A Mile Above the Rim:
‘Stuffed!’ shouted the taller boy. ‘Doobie got himself stuffed!… In yo’ face, Doobie!’
It was originally associated with sports and competition but has since evolved to a broader use for any kind of confrontation and usually used with humor.
The Wurd Turtle 