Chaotic movements within the flow of a fluid.
In coffee we use this term to describe movements in brewing water at two different scales:
1. In filter coffee brewing, when the flow of brewing water is sufficient to disrupt the coffee bed and create agitation.
2. In an espresso القُرص or during drawdown of a filter brew, when eddies occur at a micro scale in the flow of water through gaps between particles in the coffee bed; the opposite of laminar flow.