The Collaborative International Dictionary of English v.0.48:

Adjustable \Ad*just"a*ble\, a.
   Capable of being adjusted.
   [1913 Webster]

WordNet (r) 3.0 (2006):

adjustable
    adj 1: capable of being changed so as to match or fit;
           "adjustable seat belts"
    2: capable of being regulated; "adjustable interest rates"

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "adjustable":
   able to adapt, acquiescent, adaptable, adaptive, all-around,
   alterable, alterative, ambidextrous, amphibious, changeable,
   checkered, complaisant, compliant, conformable, ever-changing,
   flexible, fluid, generally capable, impermanent, kaleidoscopic,
   malleable, many-sided, metamorphic, mobile, modifiable, movable,
   mutable, nonuniform, obedient, other-directed, permutable, plastic,
   pliant, protean, proteiform, resilient, resourceful, rubbery,
   submissive, supple, tractable, transient, transitory, two-handed,
   variable, versatile