The Collaborative International Dictionary of English v.0.48:

Vortex \Vor"tex\, n.; pl. E. Vortexes, L. Vortices. [L.
   vortex, vertex, -icis, fr. vortere, vertere, to turn. See
   Vertex.]
   [1913 Webster]
   1. A mass of fluid, especially of a liquid, having a whirling
      or circular motion tending to form a cavity or vacuum in
      the center of the circle, and to draw in towards the
      center bodies subject to its action; the form assumed by a
      fluid in such motion; a whirlpool; an eddy.
      [1913 Webster]

   2. (Cartesian System) A supposed collection of particles of
      very subtile matter, endowed with a rapid rotary motion
      around an axis which was also the axis of a sun or a
      planet. Descartes attempted to account for the formation
      of the universe, and the movements of the bodies composing
      it, by a theory of vortices.
      [1913 Webster]

   3. (Zool.) Any one of numerous species of small Turbellaria
      belonging to Vortex and allied genera. See Illustration
      in Appendix.
      [1913 Webster]

   Vortex atom (Chem.), a hypothetical ring-shaped mass of
      elementary matter in continuous vortical motion. It was
      conveniently regarded in certain early mathematical models
      as the typical form and structure of the chemical atom,
      but is no longer considered a useful model, having been
      superseded by quantum mechanics.

   Vortex wheel, a kind of turbine.
      [1913 Webster +PJC]