An "open staircase" refers to a staircase that does not have walls or barriers on the sides or underneath the steps. It means that you can see through and around the staircase, providing a more open and spacious feel.
Sentences with «open staircase»
Large kitchen with open staircase to partially finished basement. (redfin.com)
As you enter the home, the foyer opens to the large open staircase accessing the home. (vacationbeach.rentals)
2nd floor open staircase with master bedroom & private bathroom. (nadiasells.com)