Source : Webster's Revised Unabridged Dictionary (1913)

Sext \Sext\, n. [L. sexta, fem. of sextus sixtt, fr. sex six:
   cf. F. sexte.] (R.C.Ch.)
   (a) The office for the sixth canonical hour, being a part of
       the Breviary.
   (b) The sixth book of the decretals, added by Pope Boniface
       VIII.

Source : WordNet®

sext
     n : the fourth of the seven canonical hours; about noon