Plenum may refer to: Plenum chamber, a chamber intended to contain air, gas, or liquid at positive pressure Plenism, or Horror vacui (physics) the concept that "nature abhors a vacuum" Plenum (meeting), a meeting of a deliberative assembly in which all members are present; contrast with quorum Plenum space, enclosed spaces (in buildings) used for airflow Plenum cable, electrical wire permitted in plenum spaces per building codes Plenum Publishing Corporation, a publisher of scientific books and journals Plenum (physics), a space completely filled with matter Undergravel filters, in aquarium filtration, an open space under a layer of gravel or sand Air-mixing plenum, a place where ducts meet See also Plenary (disambiguation), the related adjective