The Collaborative International Dictionary of English v.0.48:
Toxicity \Tox*ic"i*ty\, n. The quality or state of being toxic or poisonous; poisonousness. [Webster 1913 Suppl.]WordNet (r) 3.0 (2006):
toxicity n 1: the degree to which something is poisonous 2: grave harmfulness or deadliness [syn: perniciousness, toxicity]