a vertical pipe in a building
"The plumber had to climb inside the riser to fix the leak in the fourth-floor bathroom."
structural member consisting of the vertical part of a stair or step
"The builder replaced the rotten riser to ensure the new staircase met safety codes."
Someone or something which rises.
"As the sun began to set, the mountain riser cast a long shadow across the valley floor."
A surname.
"The Riser family has lived in that small coastal town for three generations."