'Doubtable' definitions:

Definition of 'Doubtable'

From: GCIDE

Doubtable \Doubt"a*ble\, a. [OF. doutable, L. dubitabilis, from dubitare. Cf. Dubitable.]
1. Capable of being doubted; questionable. [1913 Webster]
2. Worthy of being feared; redoubtable. [Obs.] [1913 Webster]