Definitions
1.nounA space that is completely filled with matter.
2.nounA state of fullness, a great quantity (of something).
3.nounA legislative meeting (especially of the Communist Party) in which all members are present.
4.nounAn enclosed space having greater than atmospheric pressure.
5.nounThe space above a false ceiling used for cables, ducts etc.
6.nounA type of network cabling which satisfies plenum-ratings issued by the National Electrical Code. These cables produce less smoke and fumes in the event of fire.