Definition
A code used in METAR reports to indicate that the wind direction is variable and cannot be reliably reported as a single direction. It is used when the wind speed is 6 knots or less, or when the wind direction varies by 60 degrees or more and the speed is greater than 6 knots.
Plain English
VRB means the wind is shifting around so much that the report can't pin it down to one direction. Instead of giving a number, the report just says the wind is variable.
Context Anchor
Seen in METAR aviation weather reports in the wind group, especially with light, shifting winds.
Derivation
VRB is simply a shortened form of 'variable.' The METAR format uses three-letter codes throughout, so 'variable' becomes VRB to fit the standard wind-group structure.
Why Pilots Care
Variable winds affect crosswind calculations and runway choice for takeoff and landing.
Intuition Check
Do not read VRB as a compass direction. It means the report is not giving one steady wind direction.
Example Sentence 1
The METAR showed VRB03KT, so the tower cleared traffic for whichever runway worked best.
Example Sentence 2
With VRB winds at 5 knots, the tower cleared the aircraft to land on runway 18.