1. Fluid dynamics applied to liquids; such as, water, alcohol, oil, and blood.
2. The branch of science that deals with the dynamics of fluids; especially, incompressible fluids, in motion.
3. The dynamics of fluids in motion.
4. The branch of fluid dynamics that deals with liquids, including hydrostatics and hydrokinetics. Also called hydromechanics.
5. A branch of physics that deals with the motion of fluids and the forces acting on solid bodies immersed in fluids and in any motion relative to them.

The science of mechanics which relates to fluids or which deals with the laws of motion and action of nonelastic fluids, whether as investigated mathematically, or by observation and experiment; the principles of dynamics, as applied to water and other fluids.

The word is sometimes used as a general term, including both hydrostatics and hydraulics, together with pneumatics and acoustics.