riser
riser, 1
1. The vertical face of a stair step.
2. Any upright face, as of a seat, platform, etc.
3. A platform on the stage of a theater or concert hall on which a performer is placed.
4. A water-supply, drainage, gas, steam, or vent pipe which extends vertically, one full story or more, to service several branches or a group of fixtures.
5. An electrical cable which extends vertically, one full story or more, to distribute electrical power to electric panels on the different floors of a building.
6. A duct, which extends vertically, one full story or more, to distribute air to branch ducts on the different floors of a building.
7. A vertical supply pipe for a fire sprinkler system.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.