Source : Webster's Revised Unabridged Dictionary (1913)

Parasang \Par"a*sang\, n. [L. parasanga, Gr. ?, from Old
   Persian; cf. Per. farsang.]
   A Persian measure of length, which, according to Herodotus
   and Xenophon, was thirty stadia, or somewhat more than three
   and a half miles. The measure varied in different times and
   places, and, as now used, is estimated at from three and a
   half to four English miles.