A euphemism for selling out, for moving (or attempting to move) deliberately from a niche market to the mainstream. It usually means divesting one's self of the qualities that made for success in the niche market. A Will Smith or Shania Twain does it from square one, so there's not the sort of disappointment that, say, a prog fan (back in the day) might have had upon seeing an Asia video, or that of an old fan of The Stooges upon seeing today's user-friendly iteration of Grandpa Iggy Pop.