WordWeb Online

1. Not usual, common or ordinary
   "a scene of unusual beauty"; "a man of unusual ability"; "cruel and unusual punishment"; "an unusual meteorite"
    
2. Not commonly encountered
   "two-career families are no longer unusual"
    
3. Being definitely out of the ordinary and unexpected; slightly odd or even a bit weird
   - strange, oddball

See also: antic [archaic], crazy, curious, different, eerie, eery, exotic, extraordinary, fantastic, fantastical, freaky [informal], funny, gothic, grotesque, odd, oddish, other, out of the ordinary, out of the way, out-of-the-way, peculiar, quaint, queer, rum [Brit, informal], rummy [Brit, archaic, informal], singular, spooky [informal], unaccustomed, uncommon, unique, usualness, weird

Antonym: familiar, usual

Encyclopedia: Unusual