VIRTUAL PAGE

(1) In virtual storage systems, a fixed-length block of instructions, data, or both, that is the unit of transference between between central storage and external page storage.

(2) In virtual storage systems, "paging" is to transfer instructions, data, or both, between central storage and external storage.
Source: IBM - z/OS Glossary of terms and abbreviations
Related terms: "Central storage" aka "Main storage" aka [real] Memory;

"External storage" aka "Disk storage" aka "Page storage" aka "Virtual memory".