Wiktionary
ceilingless
a. Without a ceiling.
Usage examples of "ceilingless".
If she could reach it she could rest, safe on the floor of this tiny, three-sided, ceilingless room.
They were in a steep-roofed, ceilingless structure--a sort of pavilion perhaps a hundred feet long, open beneath the eaves to air and moonlight.
There were no sweeping terraces or pools or stretches of lawn, only a maze of enclosed spaces like ceilingless rooms.