I was recently in italy in a high class hotel restaurant and after the waiter served me wine I said "grazie" and he returned something that sounded like "Grazie bui" (or "Grazie piu" but I think it was the first one).
I never heard that before. Normally I get an answer like "prego" or similar. What does "Grazie bui" mean? According to wikitionary "bui" could be the plural of "buio" meaning "darkness" or "dark" but that wouldn't match up I believe.