fru'austumu fu'ivla

x1 is a frustum/cone/cylinder/pyramid made of material x2 with larger base x3 and at-most-as-large base x4, with other characteristics x5.

x4 cannot be larger in hyperarea than x3. A cone and a pyramid are degenerate frusta with exactly one base (x4) being exactly a point (the apex); a line segment is a doubly-degenerate frustum with x3 (and therefore x4) being a point. The bases should typically be approximately parallel to one another; they need not be perpendicular to their axis. Except possibly when at least one base is a point, they will be (apprpximately) geometrically similar to one another (having the same cross-section along parallel planes wrt the axis, modulo scale/size, which will nonetheless be multiplied by a uniform factor in all 'dimensions'). A round base will produce, approximately, a circular cone or a (circular) cylinder.

In notes:

x1 is a generalized cylinder (see notes for details) of form/shape x2.