air cushion

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Trapped air that supports an object a short distance above a surface.
• noun An inflatable cushion.

from The Century Dictionary.

• noun A bag made of an air-tight fabric used when inflated with air as a cushion for a seat.
• noun Same as air-bag.
• noun A ball or cylinder (usually of india-rubber) filled with air and placed in a water-pipe, to act as a cushion for the water, or to receive the pressure or shock caused by a sudden stoppage of its flow, or by the expansion of the water in freezing.
• noun Same as air-spring or pneumatic spring.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a layer of trapped air that supports a hovercraft
• noun a shock absorber that uses an air chamber
• noun a rubber or plastic inflatable cushion

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the trapped air that supports a hovercraft a short distance above the water or ground
• noun a cushion usually made of rubber or plastic that can be inflated
• noun a mechanical device using confined air to absorb the shock of motion