The Collaborative International Dictionary of English v.0.48:

Socialize \So"cial*ize\, v. t.
   1. To render social.
      [1913 Webster]

   2. To subject to, or regulate by, socialism.
      [1913 Webster]

WordNet (r) 3.0 (2006):

socialize
    v 1: take part in social activities; interact with others; "He
         never socializes with his colleagues"; "The old man hates
         to socialize" [syn: socialize, socialise]
    2: train for a social environment; "The children must be
       properly socialized" [syn: socialize, socialise]
    3: prepare for social life; "Children have to be socialized in
       school" [syn: socialize, socialise]
    4: make conform to socialist ideas and philosophies; "Health
       care should be socialized!" [syn: socialize, socialise]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "socialize":
   acculturate, advance, ameliorate, amend, annex, associate, attach,
   better, boost, bring forward, civilize, collectivize, commandeer,
   communalize, communize, confiscate, democratize, distrain, edify,
   educate, elevate, emend, enhance, enlighten, enrich, expropriate,
   fatten, favor, forward, foster, fraternize, garnish, get out,
   get together, go out, go straight, impound, impress, improve,
   improve upon, lard, levy, lift, make an improvement, meliorate,
   mend, mingle, mix, nationalize, nurture, politicize, press,
   promote, raise, refine upon, reform, replevin, replevy,
   republicanize, sequester, sequestrate, straighten out, transfigure,
   transform, upgrade, uplift