a unit of absorbed ionizing radiation equal to 100 ergs per gram of irradiated material
"The physicist carefully calibrated the Geiger counter to measure the exact rad dosage received by the experimental samples."
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)
"The surveyor calculated that the turn required exactly one radian, which is approximately fifty-seven point three degrees."
A non-SI unit of absorbed dose of radiation, equal to 0.01 gray.
"The software team adopted RAD to significantly shorten the project timeline."
Initialism of rapid application development.
In plain English: A rad is an old unit used to measure how much radiation energy hits your body, though scientists mostly use different units now.
"His new skateboard deck was pretty rad, and everyone at school wanted to borrow it for a while."
Usage: Use the noun rad specifically when referring to older scientific measurements of absorbed ionizing radiation that are not part of the modern SI system. It is often encountered in historical medical records or legacy equipment specifications where values must be converted to grays for current standards.
Clipping of radical; excellent
"That new roller coaster is totally rad."
In plain English: Rad is slang for something that is really cool, awesome, or exciting.
"The new skate ramp at the park is totally rad."
Initialism of Radiation Assessment Detector (a scientific instrument of the Mars Science Laboratory onboard the Curiosity rover at Mars.)
"The RAD instrument on the Curiosity rover measures radiation levels to ensure the safety of future human explorers."