Klein bottle

noun2

1. •
   The closed manifold obtained by identifying the boundary components of the annulus so that the resultant surface is nonorientable.

   • At this level Atman and Brahman are like a Klein bottle or a Möbius strip: there is no edge where one can say that this is Atman, but this is Brahman. — 1981
2. •
   A physical bottle, usually of blown glass, made to resemble said shape.