Source : Webster's Revised Unabridged Dictionary (1913)

Sivan \Si"van\, n. [Heb. s[=i]v[=a]n.]
   The third month of the Jewish ecclesiastical year; --
   supposed to correspond nearly with our month of June.

Source : WordNet®

Sivan
     n : the ninth month of the civil year; the third month of the
         ecclesiastical year in the Jewish calendar (in May and
         June) [syn: {Siwan}]