The product of being calm.
The state of being calm; tranquillity; silence.
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.
The state or fact of being turbulent or agitated; tempestuousness, disturbance.
An instance or type of such state or disturbance.