The Collaborative International Dictionary of English v.0.48:

Inadequate \In*ad"e*quate\, a. [Pref. in- not + adequate: cf. F.
   inad['e]quat.]
   Not adequate; unequal to the purpose; insufficient;
   deficient; as, inadequate resources, power, conceptions,
   representations, etc. --Dryden. -- In*ad"e*quate*ly, adv.
   -- In*ad"e*quate*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inadequateness
    n 1: unsatisfactoriness by virtue of being inadequate [syn:
         inadequacy, inadequateness] [ant: adequacy,
         adequateness]