Strong’s Greek
G552 — apeiros
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἄπειρος
apeiros — pronounced ap'-i-ros
from 1 (as a negative particle) and 3984; inexperienced, i.e. ignorant:--unskilful. see GREEK for 1 see GREEK for 3984
1 occurrence in the KJV.
Hebrews 5:13
For every one that useth milk is unskilful in the word of righteousness: for he is a babe.