Z-buffer
From The Glossary of Digital Photography
The video memory area that stores the depth information, or z-axis, of each pixel for three-dimensional images. See also HYPER Z™ III; Hierarchical z

ONLINE GLOSSARY OF DIGITAL PHOTOGRAPY
The video memory area that stores the depth information, or z-axis, of each pixel for three-dimensional images. See also HYPER Z™ III; Hierarchical z