The Collaborative International Dictionary of English v.0.48:

Flexibility \Flex`i*bil"i*ty\, n. [L. flexibilitas: cf. F.
   flexibilite.]
   The state or quality of being flexible; flexibleness;
   pliancy; pliability; as, the flexibility of strips of
   hemlock, hickory, whalebone or metal, or of rays of light.
   --Sir I. Newton.
   [1913 Webster]

         All the flexibility of a veteran courtier. --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

flexibility
    n 1: the property of being flexible; easily bent or shaped [syn:
         flexibility, flexibleness] [ant: inflexibility,
         inflexibleness]
    2: the quality of being adaptable or variable; "he enjoyed the
       flexibility of his working arrangement" [syn: flexibility,
       flexibleness] [ant: inflexibility, rigidity,
       rigidness]
    3: the trait of being easily persuaded [syn: tractability,
       tractableness, flexibility] [ant: intractability,
       intractableness]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "flexibility":
   Renaissance man, Renaissance versatility, accommodation, accord,
   accordance, acquiescence, adaptability, adaptation, adaption,
   adjustability, adjustment, agreeability, agreeableness, agreement,
   all-roundedness, alterability, ambidexterity, amenability,
   bendability, biddability, bounce, bounciness, buoyance, buoyancy,
   changeability, changeableness, changefulness, compliableness,
   compliance, conformance, conformation other-direction, conformity,
   congruity, consistency, convenience, conventionality,
   correspondence, docility, ductibility, ductility, elasticity,
   extendibility, extensibility, facility, feasibility, fictility,
   flexility, flexuousness, fluidity, formativeness, give, handiness,
   harmony, impermanence, impressionability, keeping, limberness,
   line, litheness, liveliness, malleability, manageability,
   manageableness, maneuverability, many-sidedness, mobility,
   modifiability, moldability, movability, mutability, nonstrictness,
   nonuniformity, obedience, observance, orthodoxy, permutability,
   plasticity, pliability, pliancy, practicality, rebound,
   receptiveness, reconcilement, reconciliation, resilience,
   resiliency, responsiveness, rubberiness, sensibility,
   sensitiveness, sequacity, servility, snap, spring, springiness,
   stretch, stretchability, stretchiness, strictness, submissiveness,
   subservience, suppleness, susceptibility, tensileness, tensility,
   tone, tonicity, tonus, tractability, tractility, traditionalism,
   transience, transitoriness, unaustereness, undemandingness,
   unharshness, uniformity, unsevereness, unsternness, unstrictness,
   untroublesomeness, versatility, wieldableness, wieldiness,
   willowiness, yieldingness