Klein bottle
WordNet
noun
(1) A closed surface with only one side; formed by passing one end of a tube through the side of the tube and joining it with the other end
WiktionaryText
Etymology
Named after German mathematician Felix Klein (1849-1925) who first described such a surface in 1882. "Bottle" seems to have come from a misreading or mistranslation of German Fläche as Flasche (the latter meaning bottle).
Noun
- A two-dimensional enclosed surface which doesn't have a distinct "inside" and "outside" (in a similar way that a Möbius strip has only one side).