A business process definition metamodel is like a Lego set that businesses use to build their own custom processes. This 'Lego set' has different pieces or components (called nodes) that are connected to each other and can be rearranged in many different ways to build different processes. The nodes represent different steps or activities of a process and they are connected by arrows that signify the flow of the process. This helps businesses build their own processes to accomplish whatever task they need in an efficient and organized way.