Mixing usually implies the taking of two or more separate phases, such as a fluid and a powdered solid or two fluids, and causing them to be randomly distributed through one another.
Agitation refers to forcing a fluid by mechanical means to flow in a circulatory or other pattern inside a vessel
Blending: Agitation of two miscible liquid phase
Suspension: Suspending solid particles into liquid.
Dispersion: Dispersing a gas through the liquid in the form of small bubbles.