Originally (depreciative): typical of, or associated with, working-class white (especially Afrikaans-speaking) people of relatively low social status; common; trashy. Now frequently: designating a style of music, dress, or youth culture ironically, knowingly, or ostentatiously appropriating aspects of this. Also as noun: this music or the dress and lifestyle associated with it.
1990s. From Afrikaans zef, respelling of zeph- (in Ford Zephyr, the name of a car popular with white working-class South Africans).