Turbulence, in air travel, is a period of rough air patches which a plane travels through. Though almost always not dangerous, it is just about the top fear for many travelers. Simply put, it is the unsteady or violent movement of air; in air travel, it may be the unsteady or violent movement of the plane through the air.
Turbulence has been categorized into some more specific terms. Wake turbulence is a form that follows the plane, as the jetwash causes such in the airplane’s wake. A more dangerous and less predictable form is clear-air turbulence.