Definition
Irregular motion of the atmosphere caused by air moving in eddies, currents, or sudden vertical and horizontal gusts. Turbulence is reported in four intensity categories — light, moderate, severe, and extreme — based on the effect it has on the aircraft and its occupants.
Plain English
Bumpy, unsettled air. Instead of flowing smoothly, the air is moving in jumbled pockets that push the airplane around.
Context Anchor
Pilots encounter turbulence in weather briefings, pilot reports, forecasts, near mountains, near storms, close to the ground on windy days, and behind other aircraft.
Derivation
From the Latin 'turbulentus,' meaning 'restless' or 'disturbed,' from 'turba' meaning 'crowd' or 'commotion.' The image is of air that is stirred up and disorderly rather than flowing in a smooth, organized stream.
Why Pilots Care
Affects aircraft control, passenger comfort, and in strong cases can stress the airframe; pilots reduce speed and may divert to smoother air.
Analogy
It is like driving a car over uneven pavement. The car is still controllable, but the ride is no longer smooth and you adjust your speed to protect the vehicle and people inside.
Grounding Statement
Think of a boat on choppy water versus glass-smooth water — same boat, very different ride. Turbulence is the atmosphere's version of chop.
Intuition Check
Do not assume turbulence means a thunderstorm or that the airplane is out of control. Turbulence means the air is moving unevenly; it can happen in clear weather, and its effect depends on how strong it is.
Example Sentence 1
The pilot reported moderate turbulence at 8,000 feet and requested a climb to 12,000 to find smoother air.
Example Sentence 2
The weather briefing noted light turbulence possible below 6000 feet due to surface heating.