Source : Webster's Revised Unabridged Dictionary (1913)

Lethality \Le*thal"i*ty\ (l[-e]*th[a^]l"[i^]*t[y^]), n. [Cf. F.
   l['e]thalit['e].]
   The quality of being lethal; mortality.

Source : WordNet®

lethality
     n : the quality of being deadly [syn: {deadliness}]