Green’s Dictionary of Slang

(US campus) a student who is not a fraternity or sorority member; thus adj. geedy, unaffiliated to a fraternity or sorority.

1964		Poston ‘Problems in the Study of Campus Sl.’ in AS XXXIX:2 119: The familiar B.M.O.C. ‘big man on campus’ may have a broader area of response than its opposite G.D.I., or ‘God-damned independent’.
1987		Eble Campus Sl. Fall.
1989		P. Munro Sl. U.
2016		C. Eble UNC-CH Campus Sl. Spring 2016 4: GEED — < g.d.i, < god damned independent someone not affiliated with a fraternity or sorority. Usually said of males. GEEDY — not affiliated with a fraternity or sorority; unconventional in appearance or behavior.