(computer hardware) An individual computer processor, in the sense when several processors (called cores or CPU cores) are plugged together in one single integrated circuit to work as one (called multi-core processor).
(engineering) The material between surface materials in a structured composite sandwich material.
(automotive, machinery, aviation, marine) A deposit paid by the purchaser of a rebuilt part, to be refunded on return of a used, rebuildable part, or the returned rebuildable part itself.