[le.thal] adj [L letalis, lethalis, fr. letum death] (1604) 1 a: of, relating to, or causing death "death by ~ injection" b: capable of causing death "~ chemicals"
2: gravely damaging or destructive: devastating "a ~ attack on his reputation" syn see deadly -- le.thal.i.ty n -- le.thal.ly adv
[2]lethal n (1917) 1: an abnormality of genetic origin causing the death of the organism possessing it
2: lethal gene