From The Collaborative International Dictionary of English v.0.48 :
Oligarchic \Ol`i*gar"chic\, Oligarchical \Ol`i*gar"chic*al\, a.
[Gr. ?: cf. F. oligarchique. See Oligarchy.]
Of or pertaining to oligarchy, or government by a few.
"Oligarchical exiles." --Jowett (Thucyd.).
[1913 Webster]
From WordNet (r) 3.0 (2006) :
oligarchical
adj 1: of or relating to or supporting or characteristic of an
oligarchy [syn: oligarchic, oligarchical]