What does "riser" mean?

Riser: (Arch.) (a) The upright piece of a step, from tread to tread. Hence: (b) Any small upright face, as of a seat, platform, veranda, or the like.

Additional senses

  1. 2.(Mining) A shaft excavated from below upward.
  2. 3.(Founding) A feed head. See under Feed, n.

Sources