A loop with a twist in it that is nonorientable. If you were to travel from a starting point on the strip and moved the full length of the strip you would end up moving along both sides without crossing an edge.
See also:
 Slavoj Žižek used the analogy of a mobious strip (as well as a Klein bottle) to represent the spectrum of ideology where continuing to the extremes results in the complete opposite of the core belief.
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A righthalfplane zero is when the exponential growth rate of an input does not affect the output. For example, eating ice cream increases happiness but creates more unhappiness so you eat more ice cream to make up for it and so on until there is no ice cream anywhere.

A theory that the universe is actually finite due to having a nontrivial topology (i.e. like a mobius strip).