Source : Webster's Revised Unabridged Dictionary (1913)

Phreatic \Phre*at"ic\, a. [F. phr['e]atique, from Gr. ?, ?, a
   well.] (Geol.)
   Subterranean; -- applied to sources supplying wells.

Source : WordNet®

phreatic
     adj : of or relating to ground water