Source : Webster's Revised Unabridged Dictionary (1913)

Happy \Hap"py\, a. [Compar. {Happier}; superl. {Happiest}.]
   [From {Hap} chance.]
   1. Favored by hap, luck, or fortune; lucky; fortunate;
      successful; prosperous; satisfying desire; as, a happy
      expedient; a happy effort; a happy venture; a happy omen.

            Chymists have been more happy in finding experiments
            than the causes of them.              --Boyle.

   2. Experiencing the effect of favorable fortune; having the
      feeling arising from the consciousness of well-being or of
      enjoyment; enjoying good of any kind, as peace,
      tranquillity, comfort; contented; joyous; as, happy hours,
      happy thoughts.

            Happy is that people, whose God is the Lord. --Ps.
                                                  cxliv. 15.

            The learned is happy Nature to explore, The fool is
            happy that he knows no more.          --Pope.

   3. Dexterous; ready; apt; felicitous.

            One gentleman is happy at a reply, another excels in
            a in a rejoinder.                     --Swift.

   {Happy family}, a collection of animals of different and
      hostile propensities living peaceably together in one
      cage. Used ironically of conventional alliances of persons
      who are in fact mutually repugnant.

   {Happy-go-lucky}, trusting to hap or luck; improvident;
      easy-going. ``Happy-go-lucky carelessness.'' --W. Black.

Source : WordNet®

happy-go-lucky
     adj : cheerfully irresponsible; "carefree with his money";
           "freewheeling urban youths"; "had a harum-scarum youth"
           [syn: {carefree}, {devil-may-care}, {freewheeling}, {harum-scarum},
            {slaphappy}]