Source : Webster's Revised Unabridged Dictionary (1913)

Biquintile \Bi*quin"tile\, n. [Pref. bi- + quintile: cf. F.
   biquintile.] (Astron.)
   An aspect of the planets when they are distant from each
   other by twice the fifth part of a great circle -- that is,
   twice 72 degrees.