Fancy, snobbish, expensive, refined. Normally used in a derogatory or sarcastic sense. It's a rather American term, perhaps from the South? I'm not sure. I know I always like it when I come across it, as it serves to pinpoint the character who uses it and their attitude. Usually the speaker is a good-humoured, down-to-earth person.
Fact: In New Zealand we would say "poncy" (pronounced pon-see) which is derived from Ponsonby, a coastal suburb in central Auckland, nationally known for its upmarket character and slightly snobbish inhabitants. Apologies to anyone who happens to live there - I have never been able to verify these traits, but that's how we use the word.