noun

1. A non-SI unit of absorbed dose of radiation, equal to 0.01 gray.

Synonyms: rd

noun

1. In the International System of Units, the derived unit of plane angular measure of angle equal to the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle. Symbol: rad

noun

1. Anything which radiates or emits rays.

2. A device that lowers engine coolant temperature by conducting heat to the air, through metal fins.

3. (of buildings) A finned metal fixture that carries hot water or steam in order to heat a room.

adjective

1. Favoring fundamental change, or change at the root cause of a matter.

   “His beliefs are radical.”

2. Pertaining to a root (of a plant).

3. Pertaining to the basic or intrinsic nature of something.

Synonyms: primitive, fundamental

noun

1. The distance between the front and rear sights of a firearm.