jbislanu lujvo

x1 is an object that has a shape that is three-dimensional and has an axis (especially of symmetry and/or along which cross-sections are mutually similar), or which is approximately a figure of revolution, or which is approximately the result of taking a two-dimensional shape and sweeping it along a curve in a constant way; x1 is (nearly) cylindrical and is made of/has composition x2, having geometric/topological properties x3.

In notes:

x1 is an axis/center curve/extended center (or, possibly metaphorically, focus 'point') of x2 in sense x3