Webster's Revised Unabridged Dictionary · 1913

Lethal

Lethal (leth"al) , noun

[Lauric + ether + alcohol.]

(Chemistry) 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.

Lethal (lē"thal) , adjective

[Latin lethalis, letalis, from lethum, letum, death: compare French léthal.]

Deadly; mortal; fatal.
The lethal blow. — W. Richardson