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.-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.-any one of numerous species of small turbellaria belonging to vortex and allied genera.  see illustration in appendix.