disappearing stair[′dis·ə‚pir·iŋ ′ster]
A stair that can be swung up into a ceiling space.
disappearing stair, folding stair, loft ladder
A swinging stair, usually a folding ladder, which enables passage to an attic space or loft. The stair is fixed to a trapdoor which, when closed, hides the stair from viewers below.