Definition
A fuel system arrangement, controlled by a crossfeed valve, that allows fuel from one tank or side of the airplane to be fed to an engine on the opposite side. It is used in multi-engine airplanes to balance fuel load between tanks or to supply a working engine from a tank that would normally feed the other engine.
Plain English
A switch or valve that lets one engine draw fuel from the tank on the other side of the airplane.
Context Anchor
Seen in fuel system procedures, especially in multiengine airplanes, when managing which tank is supplying which engine.
Derivation
Cross (from one side to the other) plus feed (to supply). The name describes exactly what the system does: it feeds fuel across the airplane from one side to the other.
Why Pilots Care
Enables continued engine operation if a tank is low or empty and helps maintain lateral fuel balance to avoid handling problems.
Intuition Check
Crossfeed does not simply mean moving fuel from one tank into another tank. In this context, it usually means letting fuel from one side supply an engine or fuel line that normally uses the other side.
Example Sentence 1
After the right engine was secured, the pilot opened the crossfeed valve so the left engine could draw fuel from the right main tank.
Example Sentence 2
The crew used crossfeed briefly to even out the fuel load before landing.