Plain English Meaning
The thinner, lower-pressure air found at higher altitudes. The higher you go, the less the air pushes on you and on everything dissolved in your body.
Full Definition
Atmospheric pressures that are reduced compared to sea-level standard pressure, encountered as altitude increases. As a pilot climbs, the weight of the air column above decreases, and the surrounding air pressure drops accordingly. At high altitudes, these reduced pressures can allow dissolved nitrogen in body tissues to come out of solution and form bubbles, producing decompression sickness (DCS).
Context Anchor
Seen in aeromedical discussions of high-altitude , , pressure loss, and altitude-induced decompression sickness.