rad

Rad is an informal adjective meaning radical or cool; used to express enthusiasm or approval. The term rose to prominence in American slang during the late 20th century and remains recognizable, though somewhat dated, in many English-speaking communities. It is often used as an exclamation (That concert was rad) and can function as a shorthand for the word radical in casual speech.

Rad is also a unit of absorbed radiation dose in early radiology and dosimetry; it represents the amount of energy deposited by ionizing radiation per kilogram of matter. By definition, one rad equals 0.01 gray (Gy); because 1 Gy equals 100 rad, the gray is the modern SI unit. The rad was introduced in the 20th century and has largely been superseded in formal use by the gray, though it appears in older literature and in some industry contexts.

Rad is a 1986 American sports comedy film directed by Hal Needham. It centers on a teenage BMX rider who aims to compete in a major race and confronts a rival. The film has achieved cult status among BMX enthusiasts and is frequently associated with 1980s pop culture.