The Collaborative International Dictionary of English v.0.48:

Joyful \Joy"ful\, a.
   Full of joy; having or causing joy; very glad; as, a joyful
   heart. "Joyful tidings." --Shak.
   [1913 Webster]

         My soul shall be joyful in my God.       --Is. lxi. 10.
   [1913 Webster]

         Sad for their loss, but joyful of our life. --Pope.
   -- Joy"ful*ly, adv. -- Joy"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

joyful
    adj 1: full of or producing joy; "make a joyful noise"; "a
           joyful occasion" [ant: sorrowful]
    2: full of high-spirited delight; "a joyful heart" [syn:
       elated, gleeful, joyful, jubilant]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "joyful":
   animating, beaming, beatific, beatified, blessed, blissful, blithe,
   blithesome, buoyant, buxom, capering, cheerful, cheering, cheery,
   chirping, convivial, dancing, delighted, ecstatic, effervescent,
   elated, encouraging, enlivening, exhilarated, exhilarating,
   expansive, exultant, festal, festive, flushed with joy, frivolous,
   gala, gay, glad, gladdening, gladsome, gleeful, glowing, gratified,
   happy, heart-warming, heartening, hilarious, in heaven,
   in seventh heaven, inspiring, inspiriting, invigorating, jocular,
   jocund, jolly, jovial, joyous, jubilant, laughing, laughter-loving,
   leaping, light-hearted, lighthearted, merry, merrymaking,
   mirth-loving, mirthful, on cloud nine, on the loose, overjoyed,
   pleased, purring, radiant, rejoicing, risible, singing, smiling,
   smirking, sparkling, starry-eyed, sunny, thrice happy,
   tickled pink