[1] : The Collaborative International Dictionary of English v.0.48

mirthful \mirth"ful\, a.
   1. full of mirth or merriment; merry; as, mirthful children.
      1913 webster

   2. indicating or inspiring mirth; as, a mirthful face.
      1913 webster

            mirthful, comic shows.                --shak.
      1913 webster -- mirth"fully, adv. --
      mirth"fulness, n.
      1913 webster
see also:
mirth"fully mirth"fulness 

[2] : WordNet (r) 2.0

mirthful
     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, merry
     2: arousing or provoking laughter; "an amusing film with a
        steady stream of pranks and pratfalls"; "an amusing
        fellow"; "a comic hat"; "a comical look of surprise";
        "funny stories that made everybody laugh"; "a very funny
        writer"; "it would have been laughable if it hadn't hurt
        so much"; "a mirthful experience"; "risible courtroom
        antics" syn: amusing, comic, comical, funny, laughable,
         risible
see also:
gay jocund jolly jovial merry amusing 
comic comical funny laughable risible 

[3] : Moby Thesaurus II by Grady Ward, 1.0

20 moby thesaurus words for "mirthful":
   blithe, blithesome, buxom, festive, frivolous, gay, gleeful,
   hilarious, jocular, jocund, jolly, jovial, joyful, joyous,
   laughter-loving, lighthearted, merry, mirth-loving, rejoicing,
   risible

Mirthful >> M Words
Mirthful, definition of term: Mirthful
mirthful_pag1.html