(intransitive, nautical, aviation) To driftsideways or to leeward (by analogy with the movement of a crab).
(transitive) To navigate (an aircraft, e.g. a glider) sideways against an air current in order to maintain a straight-line course.
(obsolete, World War I), to fly slightly off the straight-line course towards an enemy aircraft, as the machine guns on early aircraft did not allow firing through the propeller disk.