1. rad, radioactivity unit

usage: a unit of absorbed ionizing radiation equal to 100 ergs per gram of irradiated material

2. radian, rad, angular unit

usage: the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)

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See also: rad (Dictionary)