Fly-boy Share definition Flag Someone under the age of 18 who has either loads of cash on them during school, wears the most popular clothes and loves or owns a Bugatti. Classmate: You're such a fly-boy, mate. Fly-boy: I know. Fly-boy by spbman1234 June 12, 2014 0 0 Get merch Get the Fly-boy mug. Buy Now — $32.95 See more merch