from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A unit of angular measure equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle, approximately 57°17ʹ44.6〞. See Table at measurement.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. 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
from the GNU version of the Collaborative International Dictionary of English
- n. An arc of a circle which is equal to the radius, or the angle measured by such an arc.
from The Century Dictionary and Cyclopedia
- n. The angle subtended at the center of a circle by an are equal in length to the radius. Also called the unit angle in circular measure. It is equal to 57° 17′ 44″. 80625 nearly.
- n. A unit of angular velocity equivalent, approximately, to 0.15916 revolutions per second, or, strictly, to revolutions per second: in full, radian per second.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. 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)
radi(us) + -an1.(American Heritage® Dictionary of the English Language, Fourth Edition)
From radi(us) + -an (Wiktionary)