The Collaborative International Dictionary of English v.0.48:

Availability \A*vail`a*bil"i*ty\, n.; pl. Availabilities.
   1. The quality of being available; availableness.
      [1913 Webster]

   Note: The word is sometimes used derogatively in the sense of
         "mere availableness," or capability of success without
         regard to worthiness.
         [1913 Webster]

               He was . . . nominated for his availability.
                                                  --Lowell.
         [1913 Webster]

   2. That which is available.
      [1913 Webster]

WordNet (r) 3.0 (2006):

availability
    n 1: the quality of being at hand when needed [syn: handiness,
         accessibility, availability, availableness] [ant:
         inaccessibility, unavailability]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "availability":
   access, accessibility, actual presence, applicability,
   approachability, being here, being there, come-at-ableness,
   effectiveness, efficacy, efficiency, existence, functionality,
   getatableness, gettableness, helpfulness, hereness, immanence,
   immediacy, indwellingness, inherence, obtainability,
   obtainableness, occurrence, openness, operability, penetrability,
   perviousness, physical presence, practicability, practical utility,
   practicality, presence, procurability, procurableness,
   profitability, reachableness, securableness, serviceability,
   spiritual presence, thereness, ubiety, usability, use, usefulness,
   utility, utilizability, whereness



The Free On-line Dictionary of Computing (30 December 2018):

availability

    The degree to which a system suffers degradation or
   interruption in its service to the customer as a consequence
   of failures of one or more of its parts.

   One of the components of RAS.

   (2000-08-13)