Source : Webster's Revised Unabridged Dictionary (1913)

Septuagesima \Sep`tu*a*ges"i*ma\, n. [NL., fr. L. septuagesimus
   the seventieth, fr. septuaginta seventy.] (Eccl.)
   The third Sunday before Lent; -- so called because it is
   about seventy days before Easter.

Source : WordNet®

Septuagesima
     n : the 3rd Sunday before Lent (or the 9th before Easter) [syn:
         {Septuagesima Sunday}]