riser

Concise Oxford English Dictionary © 2008 Oxford University Press:
riser/ˈrʌɪzə(r)/

▶noun

• 1 a person who habitually gets out of bed at a particular time of the morning: an early riser.

• 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.

• 5 a strip of webbing joining the harness and the rigging lines of a parachute or paraglider.