The amount of space between the leading edge and the groundline when the club is in the square address position. In general, more bounce is better for soft sand and lush grass; less bounce is better for firm sand and turf.
Some technical terms defined
CENTER OF GRAVITY (CG)
A low CG helps to launch the ball higher. It isn't always found at the geometric center.
COEFFICIENT OF RESTITUTION (COR)
CUBIC CENTIMETER (CC)
MOMENT OF INERTIA (MOI)
The USGA limit for drivers is 5,900 grams/cm².