A more thorough explanation:

Definition: Milling in transit is when a shipment is stopped at a middle point during transportation, usually to apply a manufacturing process. This may result in an additional freight charge by the carrier.

Example: A company ships a large quantity of wheat to a flour mill. During transportation, the shipment is stopped at a transit point where the wheat is milled into flour. The carrier may charge an additional fee for this process.

Explanation: The example illustrates milling in transit as the shipment is temporarily detained at a transit point for the application of a manufacturing process, which is milling the wheat into flour. This process is necessary for the wheat to be transformed into a usable product, and the carrier may charge an additional fee for this service.