Definition
A fuel system arrangement that allows fuel from a tank on one side of the aircraft to be fed to an engine on the opposite side. Cross-feed valves connect the left and right fuel supply lines so the pilot can balance fuel load between sides or supply both engines from a single tank if needed.
Plain English
A set of valves and plumbing that lets you send fuel from one side of the airplane to the engine on the other side, so you can keep the airplane balanced or keep an engine running if one tank has a problem.
Context Anchor
Seen in aircraft fuel-system descriptions, cockpit fuel selector procedures, and abnormal or emergency checklists for fuel supply or fuel imbalance situations.
Derivation
Cross simply means going from one side to the other. Feed means supplying fuel to an engine. So a cross-feed system feeds fuel across the aircraft from one side's tank to the opposite side's engine.
Why Pilots Care
Maintains lateral balance and can keep an engine running when its own tank is low or unusable.
Intuition Check
Cross-feed does not simply mean moving fuel around for convenience. In this context, it means changing the fuel path so an engine can be supplied from a tank it would not normally use.
Example Sentence 1
After noticing a fuel imbalance during cruise, the pilot opened the cross-feed to let the right engine draw from the left tank.
Example Sentence 2
After the left engine failed, the crew used the cross-feed system to supply the right engine from the left tank.