Strong's G878 — ἄφρων (adjective)
aphron (af'-rone) adj.
1. (properly) mindless, i.e. stupid
2. (by implication) ignorant
3. (specially) egotistic
4. (practically) rash
5. (morally) unbelieving
[from G1 (as a negative particle) and G5424]
KJV: fool(-ish), unwise 
Root(s): G1, G5424 
Hebrew root: φρήν
Occurrences: 11