Definition of: plenum

(plē′nəm) noun plural ·nums or ·na (-nə)
1. Fullness of matter in space; that state of things in which space is considered as fully occupied by matter, especially by absolutely continuous matter.
2. Space so considered: opposed to vacuum.
3. Any condition of fullness or plethora, or that which produces it.
4. An enclosed body of gas under greater than normal pressure.
5. A completely attended meeting, as of an association or legislative body.
6. Fullness.
—adjective Pertaining to or utilizing fullness (of air, etc.) [<L <plenus full]