Source : Webster's Revised Unabridged Dictionary (1913)

Cosecant \Co*se"cant\ (k?-s?"k?nt), n. [For co. secans, an
   abbrev. of L. complementi secans.] (Trig.)
   The secant of the complement of an arc or angle. See Illust.
   of {Functions}.

Source : WordNet®

cosecant
     n : ratio of the hypotenuse to the opposite side of a
         right-angled triangle [syn: {cosec}]