Source : Webster's Revised Unabridged Dictionary (1913)

Unusual \Un*u"su*al\, a.
   Not usual; uncommon; rare; as, an unusual season; a person of
   unusual grace or erudition. -- {Un*u"su*al*ly}, adv. --
   {Un*u"su*al*ness}, n.

Source : WordNet®

unusual
     adj 1: not usual or common or ordinary; "a scene of unusual
            beauty"; "a man of unusual ability"; "cruel and
            unusual punishment"; "an unusual meteorite" [ant: {usual}]
     2: being definitely out of the ordinary and unexpected;
        slightly odd or even a bit weird; "a strange exaltation
        that was indefinable"; "a strange fantastical mind"; "what
        a strange sense of humor she has" [syn: {strange}] [ant: {familiar}]
     3: not commonly encountered; "two-career families are no longer
        unusual"