bit plane
<graphics> (Or "bitplane") The memory in a graphic display
device which holds a complete one-bit-per-{pixel} image.
Several bit planes may be used in conjunction to give more
bits per pixel or to overlay several images or mask one with
another.
"Bit plane" may be used as a synonym for "{bitmap}", though
the latter suggests the data itself rather than the memory and
also suggests a graphics file format.
(1997-03-16)