'Harmfulness' definitions:

Definition of 'harmfulness'

From: WordNet
noun
Destructiveness that causes harm or injury [syn: harmfulness, injuriousness]
noun
The quality of being noxious [syn: harmfulness, noisomeness, noxiousness]

Definition of 'Harmfulness'

From: GCIDE
  • Harmful \Harm"ful\ (h[aum]rm"f[.u]l), a. Full of harm; injurious; hurtful; mischievous. " Most harmful hazards." --Strype. --{Harm"ful*ly}, adv. -- {Harm"ful*ness}, n. [1913 Webster]