Immeasurable rotope (no ontology)
From Hi.gher. Space
An immeasurable rotope is a rotope which has a superscript letter inside a group in its group notation definition.
The effect of this is that the orientation of a non-spherical part of a group in the rotope is undefined, making it impossible to calculate hypervolumes which depend on this orientation.
The lowest-dimensional immeasurable rotope is the three-dimensional triangular torus.