Taking an underground thing and making it mainstream, usually with corporate marketing muscle. Although it grew out of US racial politics, it also applies to phenomena like the making of mallternative out of indie rock. It needn't be pejorative: The Beatles rhythm and blues covers were a breath of fresh air for their day. But often it's an abomination: the sitcom What's Happening!! (based on the film Cooley High), Kid Rock, Pat Boone, or "soulful" boy bands.