Real Dictionary

rad in American English 1
a basic unit of an absorbed dose of radiation, equal to the absorption of 100 ergs of energy per gram of material or 0.01 joule per kilogram of material (0.01 gray or 1.1 roentgen)
noun: a unit of absorbed dose equal to 0.01 Gy

rad in American English 2
radian(s)
adjective: fine; wonderful
noun: radical

rad in American English 3
abbreviation: radian; radians

rad in British English 1
noun: a former unit of absorbed ionizing radiation dose equivalent to an energy absorption per unit mass of 0.01 joule per kilogram of irradiated material. 1 rad is equivalent to 0.01 gray

rad in British English 2
symbol for: radian

rad. in American English
abbreviation: radical

rad. in British English
abbreviation for: radical

radian in British English 2
noun: an SI unit of plane angle; the angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius. 1 radian is equivalent to 57.296 degrees and π/2 radians equals a right angle