ris·er / ˈrīzər/ • n. 1. a person who habitually gets out of bed at a particular time of the morning: late risers always exasperate early risers.2. a vertical section between the treads of a staircase.3. a vertical pipe for the upward flow of liquid or gas.4. a low platform on a stage or in an auditorium, used to give greater prominence to a speaker or performer.5. a strip of webbing joining the harness and the rigging lines of a parachute or paraglider.

riser.
1. Vertical piece between the treads of a stair.

2. Whole vertical part of a step of a stair between treads.

3. Stone in rubble-work, usually a bonder or through-stone, also called a jumper.