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®

happiest
     See {happy}

happy
     adj 1: enjoying or showing or marked by joy or pleasure or good
            fortune; "a happy smile"; "spent many happy days on
            the beach"; "a happy marriage" [ant: {unhappy}]
     2: experiencing pleasure or joy; "happy you are here"; "pleased
        with the good news" [syn: {pleased}]
     3: marked by good fortune; "a felicitous life"; "a happy
        outcome" [syn: {felicitous}]
     4: satisfied; enjoying well-being and contentment; "felt
        content with her lot"; "quite happy to let things go on as
        they are"
     5: exaggerated feeling of well-being or elation [syn: {euphoric}]
        [ant: {dysphoric}]
     6: well expressed and to the point; "a happy turn of phrase";
        "a few well-chosen words"; "a felicitous comment" [syn: {well-chosen}]
     [also: {happiest}, {happier}]