matci gismu

x₁ is a mat/pad/mattress/pallet [flat, soft, dense form] of material x₂.

Also mattress = (kicymatci). See also kicne, tapla, karda, ckana.

In notes:

ckana: x₁ is a bed/pallet of material x₂ for holding/supporting x₃ (person/object/event).
karda: x₁ is a card [small nearly-2-dimensional shape/form] of material x₂, shape x₃.
kicne: x₁ cushions x₂ with material x₃; x₁ is a cushion/pillow/pad [for x₂] of padding material x₃.
tapla: x₁ is a tile/cake [shape/form] of material x₂, shape x₃, thickness x₄.
ckabu'u: b₁ is bedcloth of material b₂.
kicymatci: m₁=k₂ is a mattress with cushion k₁.