radAn old unit used for expressing absorbed dose of ionizing radiation. One rad (rd) represents the dosage absorbed when 1 gram of matter absorbs 100 ergs of energy. Although the rad has been superseded by the gray (1 Gy = 100 rads) for many applications internationally, it is still extensively used, especially in the US. Related entry radiation unitsRelated category UNITSAlso on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |