The Collaborative International Dictionary of English v.0.48:

Spiral \Spi"ral\, n. [Cf. F. spirale. See Spiral, a.]
   1. (Geom.) A plane curve, not reentrant, described by a
      point, called the generatrix, moving along a straight line
      according to a mathematical law, while the line is
      revolving about a fixed point called the pole. Cf.
      Helix.
      [1913 Webster]

   2. Anything which has a spiral form, as a spiral shell.
      [1913 Webster]

   Equiangular spiral,a plane curve which cuts all its
      generatrices at the same angle. Same as Logarithmic
      spiral, under Logarithmic.

   Spiral of Archimedes, a spiral the law of which is that the
      generatrix moves uniformly along the revolving line, which
      also moves uniformly.
      [1913 Webster]