The Collaborative International Dictionary of English v.0.48:

Humanitarian \Hu*man`i*ta"ri*an\, n. [From Humanity.]
   1. (Theol. & Ch. Hist.) One who denies the divinity of
      Christ, and believes him to have been merely human.
      [1913 Webster]

   2. (Philos.) One who limits the sphere of duties to human
      relations and affections, to the exclusion or
      disparagement of the religious or spiritual.
      [1913 Webster]

   3. One who is actively concerned in promoting the welfare of
      humans and human societies; a philanthropist.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Humanitarian \Hu*man`i*ta"ri*an\, a.
   1. (Theol. & Ch. Hist.) Pertaining to humanitarians, or to
      humanitarianism; as, a humanitarian view of Christ's
      nature.
      [1913 Webster]

   2. (Philos.) Content with right affections and actions toward
      man; ethical, as distinguished from religious; believing
      in the perfectibility of man's nature without supernatural
      aid.
      [1913 Webster]

   3. Benevolent; philanthropic. [Recent]
      [1913 Webster]

WordNet (r) 3.0 (2006):

humanitarian
    adj 1: marked by humanistic values and devotion to human
           welfare; "a humane physician"; "released the prisoner for
           humanitarian reasons"; "respect and humanistic regard for
           all members of our species" [syn: human-centered,
           human-centred, humanist, humanistic,
           humanitarian]
    2: of or relating to or characteristic of humanitarianism;
       "humanitarian aid"
    n 1: someone devoted to the promotion of human welfare and to
         social reforms [syn: humanitarian, do-gooder,
         improver]
    2: an advocate of the principles of humanism; someone concerned
       with the interests and welfare of humans [syn: humanist,
       humanitarian]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "humanitarian":
   Robin Hood, almoner, almsgiver, almsgiving, altruistic, benefactor,
   beneficent, benevolent, benevolist, bighearted, charitable,
   do-gooder, eleemosynary, freehearted, generous, good, greathearted,
   human, humane, largehearted, philanthropic, philanthropist,
   power for good, social worker, welfare, welfare statist,
   welfare worker, welfarist, well-doer