Boutonniere/ˌbuːtnˈɪr/ Definition 1 of 2Pro Tip 1/3Special Occasions A boutonniere is typically worn during formal events or celebrations like weddings or proms. He chose a lavender boutonniere for the spring dance. Pro Tip 2/3Cultural Significance The flower choice in a boutonniere can hold cultural meaning or personal significance. His boutonniere had the national flower to honor his heritage. Pro Tip 3/3Wearing Tradition The boutonniere is traditionally worn on the left lapel of a man's jacket. He pinned the boutonniere carefully on his left lapel.