plenum [PLEE-nuhm]

-noun

  1. A full assembly,as a joint legislative assembly.

-noun

  1. The state or a space in which a gas,usually air,is contained at a pressure greater than atmospheric pressure.

-noun

  1. A space,usually above a ceiling or below a floor,that can serve as a receiving chamber for air that has been heated or cooled to be distributed to inhabited areas.

-noun

  1. The whole of space regarded as being filled with matter (opposed to vacuum).