The Collaborative International Dictionary of English v.0.48:

Mobius strip \Mo"bi*us strip`\, Mobius strip \M["o]"bi*us
strip`\, Moebius strip \Moe"bi*us strip`\, n. [From August F.
   M["o]bius, a German mathematician.]
   A mathematical object, or a physical representation of it,
   which is a two-dimensional sheet with only one surface. It is
   constructed or visualized as a rectangle, one end of which is
   held fixed while the opposite end is twisted through a 180
   degree angle and joined to the fixed end. It is a
   two-dimensional object that can only exist in a
   three-dimensional space.
   [PJC]

   Note: The moebius strip was the subject of a famous woodcut
         by M. Escher, published in 1963. See [a
         href="images]mobius.jpg">Moebius Strip II.
         [PJC]

WordNet (r) 3.0 (2006):

Mobius strip
    n 1: a continuous closed surface with only one side; formed from
         a rectangular strip by rotating one end 180 degrees and
         joining it with the other end