The Collaborative International Dictionary of English v.0.48:

Workable \Work"a*ble\, a.
   Capable of being worked, or worth working; as, a workable
   mine; workable clay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

workable
    adj 1: capable of being done with means at hand and
           circumstances as they are [syn: feasible, executable,
           practicable, viable, workable]