Short for "nouveau riche", it's a way to describe anything that is just a little too showy, garish, or ahead of its time for the occasion. Going home for Thanksgiving with a tongue piercing, a Mohawk, and a same-sex lover on a leash, for instance. Or whipping out your cigar and talking about the cool time you had practising with your semi-automatic with the Libertarian Supper Club in front of your hippie relatives, if you're a girl. None of these things are all that bad, in isolation, but it's better if you torque it back a bit.