betfu -bef-be'u- gismu

x₁ is a/the abdomen/belly/lower trunk [body-part] of x₂; [metaphor: midsection].

Also stomach (= djaruntyrango), digestive tract (= befctirango, befctirangyci'e). See also cutne, livga, canti.

In notes:

canti: x₁ is a/the gut(s)/entrails/intestines/viscera/innards/digestive system [body-part] of x₂.
cutne: x₁ is a/the chest/thorax/upper trunk/[rib cage/breast] [body-part] of x₂.
livga: x₁ is a/the liver [body-part] of x₂.
befyba'a: be₁=ba₁ is the navel / belly button (umbilicus) of be₂=ba₂.
cutyti'e: t₁ is the upper back [body-part] of c₂.
selbe'u: x₂=b₁ is the abdomen/belly/lower trunk of body x₁=b₂.
torso: x₁ is the torso (part of body excluding head and limbs) of x₂
vente: x₁ is the ventral part of body x₂
stomaxu: x₁ is a/the stomach/digestive organ of x₂