Source : Webster's Revised Unabridged Dictionary (1913)

Cheerless \Cheer"less\, a.
   Without joy, gladness, or comfort. -- {Cheer"less*ly}, adv.
   -- {Cheer"less*ness}, n.

         My cheerful day is turned to cheerles night. --Spenser.

   Syn: Gloomy; sad; comfortless; dispiriting; dicsconsolate;
        dejected; melancholy; forlorn.

Source : WordNet®

cheerlessly
     adv : in an unhappy manner; "he cheerlessly set out to do the
           task" [ant: {cheerfully}]