A boutonniere is a flower or flowers worn in a buttonhole of a man's suit. A boutonniere is a fancy decoration that you might wear to your prom.
Have you ever seen a flower poking out of a buttonhole in a man's suit? If so, you have seen a boutonniere. This is a French word for a flowers or flowers decorating a suit in this way. If you're wearing a suit and want to make it a little more colorful, a boutonniere is one way to do so. Just make sure you pick a flower for your boutonniere that goes well with your suit.