Strong’s Greek
G1425 — dusnoetos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
δυσνόητος
dusnoetos — pronounced doos-no'-ay-tos
from 1418 and a derivative of 3539; difficult of perception:--hard to be understood. see GREEK for 1418 see GREEK for 3539
1 occurrence in the KJV.
2 Peter 3:16
As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.