What is the meaning of Turbulence?

The state or fact of being turbulent or agitated; tempestuousness, disturbance.

Disturbance in a gas or fluid, characterized by evidence of internal motion or unrest.

Specifically, a state of agitation or disturbance in the air which is disruptive to an aircraft.

An instance or type of such state or disturbance.

turbulence

Source: wiktionary.org