Strong’s Greek
G5422 — phrenapatao
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
φρεναπατάω
phrenapatao — pronounced fren-ap-at-ah'-o
from 5423; to be a mind-misleader, i.e. delude:--deceive. see GREEK for 5423
1 occurrence in the KJV.
Galatians 6:3
For if a man think himself to be something, when he is nothing, he deceiveth himself.