Buoyancy/ˈbuːjənsi/ Definition 1 of 4Pro Tip 1/2Physical Context Understand 'buoyancy' is often used in discussing objects in water or air. The boat's design increases its buoyancy. Pro Tip 2/2Not Just Floating 'Buoyancy' doesn't just mean floating; it refers to the upward force too. The life jacket's buoyancy keeps you above water.