Source : Webster's Revised Unabridged Dictionary (1913)

Unsuccessful \Un`suc*cess"ful\, a.
   Not successful; not producing the desired event; not
   fortunate; meeting with, or resulting in, failure; unlucky;
   unhappy. -- {Un`suc*cess"ful*ly}, adv. --
   {Un`suc*cess"ful*ness}, n.

Source : WordNet®

unsuccessful
     adj 1: not successful; having failed or having an unfavorable
            outcome [ant: {successful}]
     2: failing to accomplish an intended result; "an abortive
        revolt"; "a stillborn plot to assassinate the President"
        [syn: {abortive}, {stillborn}]