radian: Meaning and Definition of

ra•di•an

Pronunciation: (r?'d?-un), [key]
? n. Math.
  1. the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958. Abbr.: rad
Random House Unabridged Dictionary, Copyright 1997, by Random House, Inc., on Infoplease.
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