What does airless mean?

Airless means without air, lacking air, or not containing or requiring air, used in both literal and technical senses. Literally, airless describes an environment, space, or day that has no air circulation, no fresh air, or no wind, making it feel stuffy, suffocating, close, and oppressive. For example, an airless room is a small closed room with no ventilation where air feels stale and hot, and an airless summer day is windless, calm, and still with no breeze to cool. It can also mean vacuum or outer space where there is no air. Technically, airless is used for products that operate without air. An airless paint sprayer is a paint spray system that does not use compressed air to spray paint but uses a high-pressure electric pump to force paint through a tiny nozzle, atomizing it into spray, unlike HVLP guns that need air compressor. Airless tires, also called non-pneumatic tires, are tires that do not have pressurized air inside but use solid rubber or flexible spokes to support vehicle weight, so they cannot puncture or go flat. So airless generally means absence of air, whether natural lack of breeze and ventilation, or engineered absence of air for function, emphasizing no air inside or no need for air.