The speed at which a bouncy castle is inflated.
As a bonus for you all here is some bouncy castle nomenclature:
The name given to such structures varies. They have been marketed with such names as "Bounce House", "Bouncies","Moon Bounce", "Boingalow", "Astrojump", "Moonwalk", "Jolly Jump" and "Spacewalk". "Brinca brinca", another name commonly used by Latinos, is Spanish for "jump jump". In El Paso, Texas, they are referred to as "Jumping Balloons". The term "Jolly Jumps" is often used to describe the inflatable playground structure in rural areas and some areas in the Western United States, but the term is otherwise obsolete. In Southern California, another popular term is "Closed Inflatable Trampolines", or "CITs". "Bouncy Castle" or "Inflatable Castle" are used in Ireland, the UK, New Zealand and parts of Australia, and "Jumping Castles" in Australia, Canada, South Africa and Arizona in the United States.