I. ˈlē-thəl adjective
Etymology: Latin letalis, lethalis, from letum death
Date: circa 1604
1.
a. : of, relating to, or causing death
death by lethal injection
b. : capable of causing death
lethal chemicals
2. : gravely damaging or destructive : devastating
a lethal attack on his reputation
3. : very potent or effective
a lethal fastball
also : having a high alcohol content
a lethal rum punch
Synonyms: see deadly
• le·thal·i·ty lē-ˈtha-lə-tē noun
• le·thal·ly ˈlē-thə-lē adverb
II. noun
Date: 1917
1. : an abnormality of genetic origin causing the death of the organism possessing it
2. : lethal gene