clupa -cup- gismu

x1 is a loop/circuit of x2 [material].

Also noose (= skoclupa, saljgeclupa; there is no indication of shape, but merely that the ends join/meet); closed curve defined by set of points (= cuptai). See also djine.

In notes:

x1 is a ring/annulus/torus/circle [shape/form] of material x2, inside diam. x3, outside diam. x4.
p1=c1 is a circularly ordered sequence by rule p2 on unordered set p3.