Plenum

[Sarah]

That state in which every part of space is supposed to be fullof matter; -- opposed to vacuum. G. Francis.

[Sarah]

A filled space, or the concept of space as full of something.
1 a : a space or all space every part of which is full of matter b : an air-filled space in a structure; especially : one that receives air from a blower for distribution (as in a ventilation system)
2 : a general assembly of all members especially of a legislative body
3 : the quality or state of being full

[Sarah]

end piece

[Dave Paprocki]

a meeting at which all the members of a group or organization are present:

[Zipporah Schumaker]

An assembly of all the members of a group or committee.