The Collaborative International Dictionary of English v.0.48:
Phreatic \Phre*at"ic\, a. [F. phr['e]atique, from Gr. ?, ?, a well.] (Geol.) Subterranean; -- applied to sources supplying wells. [1913 Webster] PhreneticWordNet (r) 3.0 (2006):
phreatic adj 1: of or relating to ground water