Source : Webster's Revised Unabridged Dictionary (1913)

Cheerful \Cheer"ful\, a.
   Having or showing good spirits or joy; cheering; cheery;
   contented; happy; joyful; lively; animated; willing.

         To entertain a cheerful disposition.     --Shak.

         The cheerful birds of sundry kind Do chant sweet music.
                                                  --Spenser.

         A cheerful confidence in the mercy of God. --Macaulay.

         This general applause and cheerful shout. --Shak.

   Syn: Lively; animated; gay; joyful; lightsome; gleeful;
        blithe; airy; sprightly; jocund; jolly; joyous;
        vivacious; buoyant; sunny; happy; hopeful.

Source : WordNet®

cheerful
     adj 1: being full of or promoting cheer; having or showing good
            spirits; "her cheerful nature"; "a cheerful greeting";
            "a cheerful room"; "as cheerful as anyone confined to
            a hospital bed could be" [ant: {cheerless}]
     2: pleasantly (even unrealistically) optimistic [syn: {pollyannaish},
         {upbeat}]