pilka -pil-pi'a- gismu

x₁ is a crust/rind/peel/skin/hide/outer cover of x₂.

(cf. grute, calku, skapi (pilka as a general term includes skapi), gacri)

In notes:

calku: x₁ is a shell/husk [hard, protective covering] around x₂ composed of x₃.
gacri: x₁ is a cover/[lid/top] for covering/concealing/sheltering x₂.
grute: x₁ is a fruit [body-part] of species x₂.
skapi: x₁ is a pelt/skin/hide/leather from x₂.
dalpi'a: x₁ is animal skin (including human skin), body part of x₂.
gutrypilcri: c₁=g₂=p₂ menstruates.
kapkevna: k₁ is a skin pore of pelt/skin/hide/leather k₂=s₁ from x₃=s₂.
korsenta: s₁=k₁ is a cortex (outermost layer) of structure s₃=k₂.
rutpiljdu: j₁ is a quantity of marmalade made from fruit g₁ of species g₂.
selpi'a: x₁ (inner/core "stuff") has outer layer/crust/rind/peel/skin/hide x₂.
arpi: x₁ is a scar on x₂
sepkili: x₁ is a freckle on x₂
snitatu: x₁ is a tattoo