Webster's Revised Unabridged Dictionary · 1913

Rad

Rad (rad) , noun

[radiation absorbed dose.]

A unit of measurement of the amount of ionizing radiation absorbed by an object, equal to an energy of 100 ergs per gram of irradiated material (equal to 0.01 gray).

Rad (rad) , imperfect and past participle

imp. & past participle of Read, Rede. [obsolete] — Spenser