The Collaborative International Dictionary of English v.0.48:

Altruistic \Al`tru*is"tic\, a. [Cf. F. altruiste, a. See
   Altruism..]
   Regardful of others; beneficent; unselfish; -- opposed to
   egoistic or selfish. --Bain. -- Al`tru*is"tic*al*ly,
   adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

altruistic
    adj 1: showing unselfish concern for the welfare of others [syn:
           altruistic, selfless] [ant: egocentric, egoistic,
           egoistical, self-centered, self-centred]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "altruistic":
   almsgiving, beneficent, benevolent, bighearted, bounteous,
   bountiful, charitable, committed, consecrated, considerate,
   dedicated, devoted, disinterested, eleemosynary, freehearted,
   generous, good, greathearted, humane, humanitarian, humble, kind,
   largehearted, liberal, magnanimous, modest, noble-minded,
   open-handed, philanthropic, sacrificing, self-abasing,
   self-abnegating, self-abnegatory, self-denying, self-devoted,
   self-effacing, self-forgetful, self-immolating, self-neglectful,
   self-neglecting, self-renouncing, self-sacrificing,
   self-unconscious, selfless, unacquisitive, unpossessive,
   unpretentious, unselfish, unsparing of self, welfare,
   welfare statist, welfarist