The Collaborative International Dictionary of English v.0.48:

Entertainment \En`ter*tain"ment\, n. [Cf. OF. entretenement.]
   1. The act of receiving as host, or of amusing, admitting, or
      cherishing; hospitable reception; also, reception or
      treatment, in general.
      [1913 Webster]

            The entertainment of Christ by faith. --Baxter.
      [1913 Webster]

            The sincere entertainment and practice of the
            precepts of the gospel.               --Bp. Sprat.
      [1913 Webster]

   2. That which entertains, or with which one is entertained;
      as:
      (a) Hospitality; hospitable provision for the wants of a
          guest; especially, provision for the table; a
          hospitable repast; a feast; a formal or elegant meal.
      (b) That which engages the attention agreeably, amuses or
          diverts, whether in private, as by conversation, etc.,
          or in public, by performances of some kind; amusement.
          [1913 Webster]

                Theatrical entertainments conducted with greater
                elegance and refinement.          --Prescott.
          [1913 Webster]

   3. Admission into service; service.
      [1913 Webster]

            Some band of strangers in the adversary's
            entertainment.                        --Shak.
      [1913 Webster]

   4. Payment of soldiers or servants; wages. [Obs.]
      [1913 Webster]

            The entertainment of the general upon his first
            arrival was but six shillings and eight pence. --Sir
                                                  J. Davies.

   Syn: Amusement; diversion; recreation; pastime; sport; feast;
        banquet; repast; carousal.
        [1913 Webster]

WordNet (r) 3.0 (2006):

entertainment
    n 1: an activity that is diverting and that holds the attention
         [syn: entertainment, amusement]

Moby Thesaurus II by Grady Ward, 1.0:

115 Moby Thesaurus words for "entertainment":
   Kaffeeklatsch, amusement, animal pleasure, ball, benefit, bill,
   blowout, board, bodily pleasure, carnal delight, cocktail party,
   coffee klatch, comfort, content, contentment, costume party,
   coziness, creature comforts, debut, dinner, dinner party,
   distraction, diversion, divertisement, divertissement,
   donation party, ease, endpleasure, enjoyment, euphoria, exhibit,
   exhibition, extravaganza, farewell performance, feed, festivity,
   flesh show, forepleasure, fruition, fun, garden party,
   gratification, great satisfaction, gusto, hearty enjoyment,
   hen party, house party, house-raising, housewarming,
   intellectual pleasure, joie de vivre, keen pleasure, kicks,
   lawn party, luxury, mask, masque, masquerade, masquerade party,
   meal, meat, mess, mirth, pageant, party, passe-temps, pastime,
   performance, physical pleasure, play, pleasure, premiere,
   presentation, presentment, production, quiet pleasure, recreation,
   refection, refreshment, regalement, relaxation, relief, relish,
   repas, repast, satisfaction, self-gratification, self-indulgence,
   sensual pleasure, sensuous pleasure, sexual pleasure, shindig,
   shindy, show, shower, smoker, solace, spectacle, spectacular,
   sport, spread, stag, stag party, stage presentation,
   surprise party, swan song, sweetness of life, table,
   theatrical performance, titillation, treat, tryout, voluptuousness,
   well-being, zest



The Devil's Dictionary (1881-1906):

ENTERTAINMENT, n.  Any kind of amusement whose inroads stop short of
death by injection.