Lacunar

n. pl. E. Lacunars (lå*kū"nẽrz), L. Lacunaria (lăk`&uuptack_;*nā"rĭ*å).
  1. The ceiling or under surface of any part, especially when it consists of compartments, sunk or hollowed without spaces or bands between the panels.
  2. One of the sunken panels in such a ceiling.