FAB Definition of Bicycle – a glorious two-wheeled, pedal-propelled steed of love. Also called a bike, it has handlebars for steering, a saddle for your butt, and pedals for pedaling. Not only is it a great green form of transportation, but it is also a great source of exercise and can be a social tool for hanging out with cool people. It is perhaps the world’s greatest invention. For many children it’s their first grab at freedom to travel. Going for a bike ride is a great chance to step away from problems and clear your mind. The activity or sport of riding a bike is called cycling.