'Sustainable' definitions:

Definition of 'sustainable'

(from WordNet)
adjective
Capable of being sustained

Definition of 'Sustainable'

From: GCIDE
  • Sustainable \Sus*tain"a*ble\, a. [Cf. F. soutenable, OF. soustenable.] Capable of being sustained or maintained; as, the action is not sustainable. [1913 Webster]