1. Inspiring fear
   "a tougher and more redoubtable adversary than the heel-clicking, jackbooted fanatic"
   - formidable, unnerving, doubtable [archaic] 
2. Worthy of respect or honour
   "born of a redoubtable family"

See also: alarming, reputable

• hang on
• hang together
• hang-up
• hangar
• hangar queen
• hangbird
• Hangchow
• hangdog
• hanger
• hanger-on
• hangi
• hanging
• hanging chad
• hanging fly
• Hanging Gardens of Babylon
• hanging geranium
• hanging wall
• hangman
• hangman's halter
• hangman's rope
• hangnail
• hangout
• hangover
• Hangul
• Hangzhou