資料來源 : Webster's Revised Unabridged Dictionary (1913)

Doubtable \Doubt"a*ble\, a. [OF. doutable, L. dubitabilis, from
   dubitare. Cf. {Dubitable}.]
   1. Capable of being doubted; questionable.

   2. Worthy of being feared; redoubtable. [Obs.]