Strong’s Greek
G2286 — thanasimos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
θανάσιμον
thanasimos — pronounced than-as'-ee-mos
from 2288; fatal, i.e. poisonous:--deadly. see GREEK for 2288
1 occurrence in the KJV.
Mark 16:18
They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.