definable

from WordNet (r) 3.0 (2006)

definable
    adj 1: capable of being defined, limited, or explained;
           "definable terms"; "definable rules"

from The Collaborative International Dictionary of English v.0.48

Definable \De*fin"a*ble\, a. [From {Define}.]
   Capable of being defined, limited, or explained;
   determinable; describable by definition; ascertainable; as,
   definable limits; definable distinctions or regulations;
   definable words. -- {De*fin"a*bly}, adv.
   [1913 Webster]