What is the term for reducing a semi-finished lens blank to smaller size to facilitate surfacing?

The correct answer is cribbing. In the context of lens manufacturing, cribbing specifically refers to the process of reducing a semi-finished lens blank to a smaller size. This step is crucial as it prepares the lens blank for the surfacing process, allowing for more precise fitting to the frame and improving the overall optical performance of the finished lens.

Trimming, while similar, typically refers to removing excess material or refining the edges of a lens after it has been shaped, rather than the initial size reduction from a semi-finished state. Cutting is a more general term that can refer to a variety of processes involving slicing or dividing materials, but it doesn't capture the specific action taken to prepare a lens blank for surfacing. Shaping also generally refers to the overall alteration of a lens into its final form rather than the specific preliminary step of size reduction. Therefore, cribbing is the term that specifically denotes the initial resizing process necessary for proper lens surfacing.