AskDefine | Define plenum

Dictionary Definition



1 a meeting of a legislative body at which all members are present; "the plenum will vote on all tax increases"
2 an enclosed space in which the air pressure is higher than outside [also: plena (pl)]

User Contributed Dictionary



Latin plenum, neuter of plenus ‘full’. (Influenced by Russian пленум ‘plenary session’.)


  • /'pli:nəm/


  1. A space that is completely filled with matter
    • 1974: He lay on the long stone slant down to the slapping waves, his denim shorts, sneakers, and socks under his head for a pillow, feeling the splendour of distance in all directions, the liquid silence, the plenum of aloneness. — Guy Davenport Tatlin!
  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. A type of network cabling which satisfies plenum-ratings issued by the National Electrical Code. These cables are safer in case of a fire, producing less smoke and fumes.


Derived terms



  1. A meeting where all members are present

Extensive Definition

Plenum may refer to:
  • the antithesis of a vacuum; in other words, completely-filled, positive-pressure space (see Plenism).
  • the pressures slightly above atmospheric, usually inside air or gas systems as the result of the action of fans or blowers. The plenum is measured in small units of pressure such as pascals (Pa) or ounces-force per square inch or millimeters of mercury.
  • a legislative meeting in which all members of the body are present and voting. Frequently this is used to refer to a full meeting of a Communist Party central committee. Compare to quorum.
  • a second set of bellows in devices such as hand or foot pumped organs with a weight on the top which acts as an air reservoir.
  • Plenums in buildings are enclosed spaces that are not for human occupancy, but are often used for heating, ventilating, and/or air-conditioning equipment and airflow, and for other equipment such as cables, piping, and luminaires. 'Plenum boxes' or sections are portions of HVAC air handlers or terminal units.
  • Plenum cable refers to structured cabling permitted under building codes for plenum spaces. Plenum rated cable has slow-burning, fire-resistant casing that emits little smoke
  • Plenum filtration, a method of aquarium filtration using a deep sand bed with a gap below it.

See also

plenum in Spanish: plenum

Synonyms, Antonyms and Related Words

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