DOUBTABLE
Etymology
Adjective
doubtable (comparative more doubtable, superlative most doubtable)
(uncommon) Capable of being doubted; doubtful; dubious; dubitable. See usage notes below.
(obsolete) Fearsome; redoubtable.
Usage notes
Philosophers often use "doubtable" in its literal sense of "capable of being doubted." In other scholarly and literary contexts, the more accepted direct synonym of "doubtable" is "dubitable." In all other usage, "doubtful" and "dubious" are far more common synonyms.
Synonyms
• (doubtful, dubious, capable of being doubted): uncertain
Source: Wiktionary
Doubt"a*ble, a. Etym: [OF. doutable, L. dubitabilis, from dubitare.
Cf. Dubitable.]
1. Capable of being doubted; questionable.
2. Worthy of being feared; redoubtable. [Obs.]
Source: Webster’s Unabridged Dictionary 1913 Edition