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, crushed, defeated, disappointed, discomfited, done for [informal], down-and-out, empty-handed, foiled, frustrated, goalless, gutted [Brit, informal], hitless, no-win, out, pointless, scoreless, self-defeating, success, sunk [informal], thwarted, undone, unfortunate, unfruitful, unfulfilled, unplaced, unprofitable, unrealised [Brit], unrealized, unrewarded, winless

Antonym: successful