tatami mat without a decorative cloth edge
Refers to a tatami mat that lacks the usual 'heri' (縁) border; often associated with a simple, rustic, or Zen aesthetic.
See also: へり
This tea room is laid with tatami mats without decorative edges.
Compound of 坊主 (ぼうず, 'Buddhist monk') and 畳 (たたみ, 'tatami mat'), possibly referring to the simple, unadorned style associated with monastic life.