1. n. 
A fluid-flow regime characterized by swirling or chaotic motion as the fluid moves along the pipe or conduit. The linear velocity of the fluid particles is similar regardless of position in the conduit, although particles close to the conduit walls have a lower velocity. This characteristic makes turbulent flow an efficient flow regime for the pickup and transport of solids. However, the potential for erosion may be significant, especially with abrasive fluids and a tortuous flow path.
2. n. 
A type of flow for single-phase fluids in which the velocity at any point may vary in both direction and magnitude with time. Turbulent flow is characterized by random, irregular, locally circular currents, or vortices. It occurs in straight pipes when the Reynolds number is above a critical value, corresponding to a higher production rate. Below this value, the flow is laminar. For turbulent flow in straight pipes, the velocity increases from zero at the wall of the pipe, passes through a thin layer of laminar flow to reach a near constant value over most of the pipe.
4. n. 
The random flow of a fluid in which the velocity at a certain point in the fluid varies irregularly. It occurs at a high Reynolds number, a dimensionless term related to fluid viscosity and flow rates.