WordNet (r) 3.0 (2006):

G.I.
    v 1: clean in preparation for inspection; "the soldiers GIed the
         barracks" [syn: G.I., GI]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "GI":
   Anzac, Aussie, Boche, Fritz, Heinie, Hun, Jerry, Johnny, Kraut,
   Tommy, Tommy Atkins, Yank, askari, digger, doughboy, fighter,
   fighting man, jock, man-at-arms, poilu, redcoat, sepoy, serviceman,
   swaddy, sweat, warrior



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

GI
       Gesellschaft fuer Informatik (org.)