Source : Webster's Revised Unabridged Dictionary (1913)

Unfit \Un*fit"\, a. [Pref. un- + fit.]
   Not fit; unsuitable. -- {Un*fit"ly}, adv. -- {Un*fit"ness},
   n.

Source : WordNet®

unfitness
     n 1: poor physical condition; being out of shape or out of
          condition [syn: {poor shape}, {bad condition}] [ant: {fitness}]
     2: lacking the power to perform [syn: {inability}] [ant: {ability}]
     3: the condition of not being suitable; "the judges agreed on
        his unfitness for the appointment" [ant: {fitness}]