The Collaborative International Dictionary of English v.0.48:

Rad \Rad\ (r[a^]d), n. [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).
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Rad \Rad\ (r[a^]d), obs.
   imp. & p. p. of Read, Rede. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rad
    n 1: a unit of absorbed ionizing radiation equal to 100 ergs per
         gram of irradiated material
    2: 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) [syn: radian, rad]

The Free On-line Dictionary of Computing (19 January 2023):

RAD

    Rapid Application Development.