plenum

noun6

1. •
   A space that is completely filled with matter.

   • The idea was that a thing could only move into an empty place, and that, in a plenum, there are no empty places. — 1946
2. •
   A legislative meeting (especially of the Communist Party) in which all members are present.
3. •
   An enclosed space having greater than atmospheric pressure.
4. •
   The space above a false ceiling used for cables, ducts etc.
5. •
   (figurative) A state of fullness, a great quantity (of something).
6. •
   A type of network cabling which satisfies a given plenum rating for the purpose of fire safety.