Abbreviation: CRC = "Close-Range Correction system" (Nikon)
The abbreviations means "Close-Range Correction system"
Explanation from Nikon
The Close-Range Correction (CRC) system is one of Nikon´s most important focusing innovations, for it provides superior picture quality at close focusing distances and increases the focusing range. With CRC, the lens elements are configured in a “floating element” design wherein each lens group moves independently to achieve focusing. This ensures superior lens performance even when shooting at close distances. The CRC system is used in fisheye, wideangle, Micro, and selected medium telephoto NIKKOR lenses.