In a manner that is showy, luxurious, or excessively ornate in a way that seems wasteful or pretentious.
From 'fastuous' (relating to excessive luxury or display), derived from Latin 'fastus' meaning pride or disdain, combined with the adverbial suffix '-ly'. The word evolved to describe behavior characterized by ostentatious wealth or grandeur.
This word is practically extinct in modern English, but it captures a very Roman attitude—the idea that displaying wealth too openly shows poor judgment rather than good taste. The Romans actually had a concept for this, 'fastus,' which meant the kind of arrogant pride that comes from flaunting what you have.
Complete word intelligence in one call. Free tier — 50 lookups/day.