lacunar - n.
(pl. lacunae or lacunas)
1 a hiatus, blank, or gap.
2 a missing portion or empty page, esp. in an ancient MS, book, etc.
3 Anat. a cavity or depression, esp. in bone.

lacunal adj. lacunar adj. lacunary adj. lacunose adj. [L, = pool, f. lacus LAKE(1)]