irregular prism

noun2

1. •
   a prism whose cross section is an irregular polygon

   • A right prism, having regular polygons for its terminating planes, is said to be regular ; an irregular prism is one in which the ends are irregular polygons. — 1867
2. •
   a solid that is like a prism but whose cross section is not (necessarily) a polygon

   • Irregular prisms have a cross-section with no well known shape. Some of the steel sections used in the construction industry belong to this category. — 2016