WordWeb Online

1. Not successful; having failed or having an unfavourable outcome
    
2. Failing to accomplish an intended result
   "an unsuccessful revolt"
   - abortive, stillborn

See also: attempted, defeated, disappointed, discomfited, done for, down-and-out, empty-handed, foiled, frustrated, goalless, hitless, no-win, out, ruined, scoreless, self-defeating, success, sunk, thwarted, undone, unfortunate, unfruitful, unfulfilled, unplaced, unprofitable, unrealised [Brit], unrealized, unrewarded, unsuccessfully, washed-up, winless

Antonym: successful