1. a space filled with matter, especially air or gas, as opposed to a vacuum
Usage: physics; formal
2. a full assembly or meeting of all members or participants
Usage: formal
3. an enclosed space through which air or fluid is distributed, as in heating or air-conditioning systems
Usage: technical; engineering

Examples

• In physics, a plenum is the opposite of a vacuum.
• The conference held a plenum session where all delegates could voice their opinions.
• The building's HVAC system uses a plenum to distribute air throughout the floors.
• Ancient philosophers debated whether nature abhors a plenum or a vacuum.
• The plenum of the organization met to discuss strategic changes.
• Air flows through the plenum before reaching individual vents in each room.