The Collaborative International Dictionary of English v.0.48:

Socialist \So"cial*ist\, Socialistic \So`cial*is"tic\, a.
   Pertaining to, or of the nature of, socialism.
   [1913 Webster]

WordNet (r) 3.0 (2006):

socialistic
    adj 1: advocating or following the socialist principles;
           "socialistic government" [syn: socialistic,
           socialist] [ant: capitalist, capitalistic]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "socialistic":
   Fabian, Fourieristic, Saint-Simonian, associated, collective,
   collectivistic, common, communal, communistic, commutual, conjoint,
   cooperative, general, in common, joint, mutual, phalansterian,
   popular, public, reciprocal, social, socialist, societal