What does "airless" mean?

Airless means without air, lacking air, lacking fresh air or breeze, or not requiring air for operation, depending on context. In general environmental sense, airless means having no air, no fresh air circulation, or no wind, such as an airless room that feels stuffy, suffocating, and unventilated because windows are closed and no fresh air enters, or an airless day that is windless, calm, and still with no breeze. It can also mean breathless or suffocating due to lack of oxygen. In industrial and technology context, airless has specific meanings. An airless paint sprayer is a type of paint sprayer that does not use compressed air to atomize paint but instead uses a high-pressure pump to force paint through a small tip, creating spray, unlike HVLP spray guns that use air. Airless tires, also called non-pneumatic tires, are tires that do not contain pressurized air but use solid structure or spokes to support weight, so they cannot go flat. So airless generally means without air inside or without needing air to function, whether describing stuffy environment with no ventilation, weather with no wind, tires with no air, or sprayers that operate without air compressor, emphasizing absence of air or breeze.