Unflamboyant is a word that describes someone or something that lacks flamboyance or extravagance. It can also refer to anything that is plain or simple in appearance. Antonyms for unflamboyant would be words that describe flamboyant, extravagant, or showy things. Some suitable antonyms for unflamboyant include ostentatious, flashy, flamboyant, opulent, luxurious, and extravagant. These words describe anything that is showy or attention-grabbing, which is the opposite of unflamboyant. So, when you want to describe something that is the exact opposite of unflamboyant, these antonyms will be useful in achieving that.