Definition
A technique used to counter the sideways push of a crosswind by turning the airplane's nose into the wind so that the airplane tracks straight over the desired ground path, even though the nose is not pointed along that path.
Plain English
When the wind is pushing the airplane sideways, the pilot turns the nose slightly into the wind. The airplane then moves diagonally through the air but ends up traveling in the direction the pilot wants over the ground.
Context Anchor
Used during crosswind takeoffs after liftoff, and in flight whenever wind would otherwise push the airplane off its intended path.
Derivation
Drift' means being pushed sideways off course by the wind. 'Crab' is borrowed from the sideways walk of a crab on a beach -- the airplane's nose is angled one way while it actually moves another, just as a crab's body faces forward but it scuttles sideways.
Why Pilots Care
Without it, a crosswind will push the airplane off the runway centerline, risking loss of directional control.
Analogy
Think of swimming straight across a river that has a current. To reach the point directly opposite, you have to aim slightly upstream. The crab angle is the airplane's version of aiming upstream into the wind.
Grounding Statement
Picture the airplane's nose aimed slightly into the wind while the airplane's path over the ground continues straight ahead.
Intuition Check
Crab does not mean the airplane is sliding sideways out of control. It means the nose is pointed into the wind just enough to keep the airplane's actual path straight.
Example Sentence 1
After lifting off in a strong left crosswind, the pilot established a crab into the wind to track straight out along the extended runway centerline.
Example Sentence 2
The pilot maintained the crab angle through the approach until just above the runway, then transitioned to a sideslip for touchdown.