Yaw is defined as when a ship, plane or other moving vessel swings, sways or moves back and forth across its path.(verb)
An example of yaw is an airplane swaying back and forth in a storm.
The definition of a yaw is the motion of a vessel going back and forth along its path.(noun)
An example of yaw is the motion a plane would be taking if it were swinging back and forth across its flight path.
See yaw in Webster's New World College Dictionary
Origin: ON jaga, to sway, move back and forth < or akin to Du & Ger jagen, to hunt
See yaw in American Heritage Dictionary 4
verb yawed, yaw·ing, yaws verb, intransitive
Origin: Perhaps of Scandinavian origin.
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