Plain English Meaning
The supplies a pilot brings along in case of a crash or forced landing in a remote area — things to stay alive and be found.
Full Definition
Equipment carried aboard an aircraft to keep occupants alive and aid rescue following a forced landing, ditching, or off-airport emergency. Typical items include signaling devices (mirror, whistle, flares, ELT), shelter (space blanket, tarp), fire-starting tools, water and rations, a first-aid kit, and gear suited to the terrain being flown over — such as a life raft and personal flotation devices for overwater flight, or warm clothing for mountainous or arctic routes.