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air gap

noun

Definition of air gap 

1 : an air-filled gap in a magnetic or electric circuit (as the space between the field-magnet poles and the armature in a dynamo or motor)

2 : wind gap

3 : the vertical distance between the point where water enters a plumbing fixture (as a tub) and the level at which it would overflow

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First Known Use of air gap

1878, in the meaning defined at sense 1

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The first known use of air gap was in 1878

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