• (n.) The quality of being formidable, or adapted to excite dread.
For'mi·da·ble·ness noun The quality of being formidable, or adapted to excite dread. Boyle. 
formidableness 1. Causing fear, dread, or apprehension; such as, a formidable prospect. 2. Having qualities that discourage an approach or an attack. 3. Tending to inspire awe or wonder; very impressive (having the power to excite attention, awe, or admiration).