Plain English Meaning
Diving deep or long enough that you can't just swim straight up. You have to stop on the way up at set depths so the extra gas in your body has time to come out safely.
Full Definition
A type of scuba diving in which the diver descends deep enough or stays down long enough that they cannot return directly to the surface. Instead, the diver must pause at one or more prescribed depths on the way up to allow dissolved nitrogen to leave the body gradually before surfacing.
Context Anchor
Seen in aeromedical guidance about the risk of decompression sickness after scuba diving and before flying.
Derivation
‘Decompression’ comes from Latin ‘de-’ (away from) plus ‘compress’ (press together). After breathing compressed air at depth, the diver's body must un-pressurize gradually. A ‘stop’ is exactly what it sounds like — a held depth on the ascent.
Why Pilots Care
Flying soon after decompression-stop dives raises the chance of decompression sickness because lower can cause nitrogen bubbles to form in the blood and joints.