Plain English Meaning
When wind is pushing the aircraft sideways, the pilot points the nose partly into the wind so the aircraft still travels in the direction it needs to go. The plane is angled, but its path across the ground stays straight.
Full Definition
A flight technique used to compensate for a crosswind in which the aircraft's nose is turned (yawed) into the wind so that the aircraft's actual track over the ground follows the desired course, even though the longitudinal axis is not aligned with that course.
Context Anchor
Pilots use a crab when wind is pushing the airplane sideways, especially on approach to a runway or while holding a planned course in flight.
Derivation
Named after the sideways walking motion of a crab. The aircraft is pointed one way but moving another, similar to how a crab faces one direction while scuttling sideways.
Analogy
It is like walking across a moving walkway while aiming slightly upstream so you end up straight across instead of being carried sideways.
Intuition Check
Crab does not mean the aircraft is actually flying sideways through the air like a crab walks. It means the nose is angled into the wind while the airplane’s path over the ground stays where the pilot wants it.
Example Sentence 1
With a strong crosswind from the right, the pilot held a crab into the wind to track the runway centerline on final approach.
Example Sentence 2
As the aircraft neared touchdown, the pilot removed the crab to align the fuselage with the runway direction.