The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cosecant
    n 1: ratio of the hypotenuse to the opposite side of a right-
         angled triangle [syn: cosecant, cosec]