Pepper pot skull (or salt and pepper skull) refers to a granular, mottled appearance of the calvarium with tiny hyperlucent areas. Other descriptive terms for this finding include ground glass texture and loss of differentiation between the inner and outer tables of the skull. This appearance is attributed to the resorption of trabecular bone and is seen in hyperparathyroidism. While some may use the term pepper pot skull to describe the lytic skull lesions seen in multiple myeloma, these lesions typically produce larger hyperlucent areas in the calvarium and are often referred to as "punched out" lucencies.
I recommend taking a look at the reference below - a cute reminder of all of the "food signs" in radiology.
Roche CJ, O'Keeffe DP, Lee WK, et al. Selections from the buffet of food signs in radiology. Radiographics 2002;22:1369-84.