Wordnet 3.0
ADJECTIVE (1)
1. 
 not available or accessible or at hand; 
- Example: "fresh milk was unavailable during the emergency"- Example: "his secretary said he was unavailable for comment"
The Collaborative International Dictionary of English v.0.48:
Unavailable \Unavailable\
   See available.
WordNet (r) 3.0 (2006):
unavailable
    adj 1: not available or accessible or at hand; "fresh milk was
           unavailable during the emergency"; "his secretary said he
           was unavailable for comment" [ant: available]
Moby Thesaurus II by Grady Ward, 1.0:
27 Moby Thesaurus words for "unavailable":
   abortive, beyond reach, bootless, closed forever to, closed to,
   fruitless, impenetrable, impervious, inaccessible, ineffective,
   ineffectual, lost to, out of reach, un-come-at-able, unaccessible,
   unapproachable, unattainable, unavailing, undiscoverable,
   ungettable, unobtainable, unprocurable, unproductive, unreachable,
   unsecurable, useless, vain