Definition
A fuel system design in which all fuel tanks feed into a common manifold (a shared chamber or junction), and each engine draws fuel from that manifold rather than directly from a specific tank. Any tank can supply any engine, and fuel can be transferred between tanks through the manifold. Selector valves at the manifold control which tanks are feeding and which engines are drawing.
Plain English
All the fuel tanks empty into one shared pipe, and every engine drinks from that shared pipe. So any tank can feed any engine, and the pilot can balance fuel between tanks easily.
Context Anchor
Seen in aircraft fuel system descriptions, maintenance procedures, and cockpit fuel management procedures for aircraft with more than one fuel tank and often more than one engine.
Derivation
Manifold comes from Old English manigfeald, meaning 'many-folded' or 'having many parts joined together.' In plumbing and engineering it refers to a chamber with several inlets and outlets. Cross-feed simply means fuel can flow across from one side of the aircraft to the other. Together: a many-connection junction that lets fuel cross between any tank and any engine.
Why Pilots Care
It lets crews keep engines running and balance fuel loads when a tank is low or unusable, avoiding asymmetric thrust or fuel exhaustion.
Analogy
Think of several water tanks connected to a common pipe with valves. By opening and closing the right valves, water from one tank can be sent to different outlets.
Intuition Check
Do not confuse this with the engine intake manifold. Here, manifold means a shared fuel pathway, and cross-feed means fuel can be directed across the aircraft from one tank or side to another.
Example Sentence 1
The twin's manifold cross-feed fuel system allowed the mechanic to drain all four tanks through a single sump after isolating the manifold.
Example Sentence 2
During the preflight check the mechanic verified that the manifold cross-feed fuel system could route fuel to either engine from either tank.