1. Any void space. 2. A single room in a prison or jail. 3. The anatomical units of plant tissue, including wood fibers, vessel members, and other elements of diverse structure and function. 4. One of the hollow openings in building tile or cement blocks. 5. In electrical raceways, a single, enclosed tubular space in a cellular metal floor member, the axis of the cell being parallel to the axis of the metal floor member.