1. (adj)deadly, lethal of an instrument of certain death "deadly poisons"; "lethal weapon"; "a lethal injection"
Definitions of 'lethal'
Webster 1913 Dictionary
1. (adj)lethal deadly; mortal; fatal
2. (noun)lethal one of the higher alcohols of the paraffine series obtained from spermaceti as a white crystalline solid. It is so called because it occurs in the ethereal salt of lauric acid