trixe -rix-ti'e- gismu

x1 is posterior/behind/back/in the rear of x2 which faces/in-frame-of-reference x3.

Also: x3 is the standard of orientation for x2; spine (= rixybo'u, rixybo'ukamju). See also crane, rebla, mlana, pritu, zunle.

In notes:

crane
x1 is anterior/ahead/forward/(in/on) the front of x2 which faces/in-frame-of-reference x3.
mlana
x1 is to the side of/lateral to x2 and facing x3 from point of view/in-frame-of-reference x4.
pritu
x1 is to the right/right-hand side of x2 which faces/in-frame-of-reference x3.
rebla
x1 is a/the tail/appendix [body-part] of x2; [metaphor: trailing, following portion/appendage].
zunle
x1 is to the left/left-hand side of x2 which faces/in-frame-of-reference x3.
jmarixtendo
x1 is the Achilles tendon of x2
rixybakfu
t1=b1 contains b2 wrapped with b3 to be hauled on the back of t2.
rixyselsrustu
x1 is the backyard of x2, enclosed by x3
ti'ekla
k1 withdraws to k2 from origin k3=t2 via route k4 using means/vehicle k5.
ti'erbi'o
b1 gets behind t2.
vinti'e
x1 is (in) the background of x2 by frame of reference x3
bekpi
x1 is the 'back', dorsum of body x2