The definition of rad is slang for an excellent person or thing.(adjective)
An example of rad is a bright sunny day spent with friends; a rad day.
Rad is defined as a unit of energy that has been absorbed from radiation.(noun)
An example of a rad is four doses of radiation absorbed into the skin.
See rad in Webster's New World College Dictionary
Origin: < rad(iation)
See rad in American Heritage Dictionary 4
Origin: r(adiation) a(bsorbed) d(ose).
Origin: Short for radical.
Learn more about rad