Anallagmatic curves

from The Collaborative International Dictionary of English v.0.48

Anallagmatic \An`al*lag*mat"ic\, a. [Gr. ?; 'an priv. + ? a
   change.] (Math.)
   Not changed in form by inversion.
   [1913 Webster]

   {Anallagmatic curves}, a class of curves of the fourth degree
      which have certain peculiar relations to circles; --
      sometimes called {bicircular quartics}.

   {Anallagmatic surfaces}, a certain class of surfaces of the
      fourth degree.
      [1913 Webster]