The Collaborative International Dictionary of English v.0.48:

Hypostatic \Hy`po*stat"ic\, Hypostatical \Hy`po*stat"ic*al\, a.
   [Gr. ?: cf. F. hypostatique.]
   1. Relating to hypostasis, or substance; hence, constitutive,
      or elementary.
      [1913 Webster]

            The grand doctrine of the chymists, touching their
            three hypostatical principles.        --Boyle.
      [1913 Webster]

   2. Personal, or distinctly personal; relating to the divine
      hypostases, or substances. --Bp. Pearson.
      [1913 Webster]

   3. (Med.) Depending upon, or due to, deposition or setting;
      as, hypostatic cognestion, cognestion due to setting of
      blood by gravitation.
      [1913 Webster]

   Hypostatic union (Theol.), the union of the divine with the
      human nature of Christ. --Tillotson.
      [1913 Webster]