In fluid dynamics, vortical means pertaining to a vortex or to vortices. The movement of a fluid can be said to be vortical if the fluid moves around in a circle, or in a helix, or if it tends to spin around some axis.
Vortical movement is characterized by non-zero vorticity, with vorticity defined as the curl of the flow velocity:
where v is the velocity vector field of the fluid flow.
The curl of the velocity — at a specified point of the vector field — yields a vector which points in the direction around which the fluid flow is rotating.