noun
round Zen meditation cushion
A traditional round cushion used in Zen meditation, typically made of woven bulrush leaves. Specific to Buddhist practice.
See also: 布団
座禅を組むときは座蒲の上に座ります。
When doing zazen, you sit on a round meditation cushion.
布団 is a general padded mattress or quilt for sleeping, while 座蒲 is specifically a round cushion for Zen meditation.
From 座 (sitting) and 蒲 (bulrush, cattail), referring to the traditional material. The exact historical derivation is uncertain; the spelling is conventionally associated with the meditation cushion.