The Collaborative International Dictionary of English v.0.48:

Benefaction \Ben`e*fac"tion\, n. [L. benefactio, fr. benefacere
   to do good to one; bene well + facere to do. See Benefit.]
   1. The act of conferring a benefit. --Johnson.
      [1913 Webster]

   2. A benefit conferred; esp. a charitable donation.
      [1913 Webster]

   Syn: Gift; present; gratuity; boon; alms.
        [1913 Webster]

WordNet (r) 3.0 (2006):

benefaction
    n 1: a contribution of money or assistance
    2: an act intending or showing kindness and good will [syn:
       benevolence, benefaction]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "benefaction":
   act of grace, act of kindness, alms, beneficence, benefit,
   benevolence, benignity, blessing, boon, charity, contribution,
   courtesy, favor, good deed, good offices, good turn, grace,
   kind deed, kind offices, kindly act, kindness, labor of love,
   manna, mercy, mitzvah, obligation, offering, office, service,
   turn