'Vortex ring' definitions:

Definition of 'Vortex ring'

From: GCIDE

Vortex ring \Vortex ring\ (Physics) A ring-shaped mass of moving fluid which, by virtue of its motion of rotation around an axis disposed in circular form, attains a more or less distinct separation from the surrounding medium and has many of the properties of a solid. [Webster 1913 Suppl.]