**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]