Definitions

1. noun

A staircase, especially one that is not at the front of a building, leading to the upper floors or a service area.

“The backstair led directly to the kitchen, where the staff would often take breaks.”

2. adjective

Located at the back of a building or area, especially with reference to a staircase or service area.

“The backstair entrance to the hotel was often used by staff and delivery personnel.”