When something is incredibly sweet or "hip." When someone incredibly white tries to express the fact that they are doing something cool.
Astrojax are very hippin. or
Adam:Hey Mike, what are you doing?
Mike:Playing with Astrojax.Am I hippin or what?
Adam:No Mike, your not hippin.
Cool,sweet, like good, up to date( must be said in american accent)
WOW! Your phone is so hippin girl