The Collaborative International Dictionary of English v.0.48:

Beneficial \Ben`e*fi"cial\, a. [Cf. F. b['e]n['e]ficial, LL.
   beneficialis.]
   1. Conferring benefits; useful; profitable; helpful;
      advantageous; serviceable; contributing to a valuable end;
      -- followed by to.
      [1913 Webster]

            The war which would have been most beneficial to us.
                                                  --Swift.
      [1913 Webster]

   2. (Law) Receiving, or entitled to have or receive,
      advantage, use, or benefit; as, the beneficial owner of an
      estate. --Kent.
      [1913 Webster]

   3. King. [Obs.] "A beneficial foe." --B. Jonson.
      [1913 Webster]

   Syn: See Advantage.
        [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "beneficial":
   advantageous, aidful, appropriate, auspicious, banausic,
   benevolent, benign, bon, bonny, bracing, braw, bueno, capital,
   cogent, commendable, commodious, conducive, constitutional,
   constructive, contributory, effective, efficacious, elegant,
   employable, estimable, excellent, expedient, fair, famous,
   favorable, fine, fitting, functional, furthersome, good, good for,
   goodly, grand, health-enhancing, health-preserving, healthful,
   healthy, helpful, hygeian, hygienic, invigorating, kind, laudable,
   nice, noble, of general utility, of help, of service, of use,
   pleasant, positive, practical, pragmatical, profitable, proper,
   refreshing, regal, remedial, royal, salubrious, salutary, sanitary,
   serviceable, skillful, sound, splendid, supportive, therapeutic,
   tonic, useful, utilitarian, valid, very good, virtuous,
   wholesome