pseudo-symmetry

from The Collaborative International Dictionary of English v.0.48

Pseudo-symmetry \Pseu`do-sym"me*try\, n. [Pseudo- + symmetry.]
   (Crystallog.)
   A kind of symmetry characteristic of certain crystals which
   from twinning, or other causes, come to resemble forms of a
   system other than that to which they belong, as the
   apparently hexagonal prisms of aragonite.
   [1913 Webster]