Source : Webster's Revised Unabridged Dictionary (1913)

Merry \Mer"ry\, a. [Compar. {Merrier}; superl. {Merriest}.] [OE.
   merie, mirie, murie, merry, pleasant, AS. merge, myrige,
   pleasant; cf. murge, adv.; prob. akin to OHG. murg, short,
   Goth. gama['u]rgjan to shorten; cf. L. murcus a coward, who
   cuts off his thumb to escape military service; the
   Anglo-Saxon and English meanings coming from the idea of
   making the time seem short. Cf. {Mirth}.]
   1. Laughingly gay; overflowing with good humor and good
      spirits; jovial; inclined to laughter or play; sportive.

            They drank, and were merry with him.  --Gen. xliii.
                                                  34.

            I am never merry when I hear sweet music. --Shak.

Source : WordNet®

merry
     adj 1: full of or showing high-spirited merriment; "when hearts
            were young and gay"; "a poet could not but be gay, in
            such a jocund company"- Wordsworth; "the jolly crowd
            at the reunion"; "jolly old Saint Nick"; "a jovial old
            gentleman"; "have a merry Christmas"; "peals of merry
            laughter"; "a mirthful laugh" [syn: {gay}, {jocund}, {jolly},
             {jovial}, {mirthful}]
     2: offering fun and gaiety; "a gala ball after the
        inauguration"; "a festive (or festal) occasion"; "gay and
        exciting night life"; "a merry evening" [syn: {gala(a)}, {gay},
         {festal}, {festive}]
     3: quick and energetic; "a brisk walk in the park"; "a lively
        gait"; "a merry chase"; "traveling at a rattling rate"; "a
        snappy pace"; "a spanking breeze" [syn: {brisk}, {lively},
         {rattling}, {snappy}, {spanking}, {zippy}]
     [also: {merriest}, {merrier}]

merrier
     See {merry}