| 
 radian
 
 
 
       
        
         | 1. | (noun) the unit of plane angle adopted under the System 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) |  
	 |  | Synonyms: rad |  
	 |  | Related Words: angular unit |  | 
 |  |