Strong's Definition
a primitive root; properly, to be fat, i.e. (figuratively) silly
KJV Usage: be foolish
STEPBible — Tyndale Abridged Hebrew Lexicon
כָּסַל (ka.sal) — be stupid. (Qal) to be foolish, be stupid
UBS Dictionary of Biblical Hebrew
verb · כְּסִיל · כְּסִילוּת · כֶּסֶל · כִּסְלָה · כְּסִיל · כִּסְלֹון · כְּסָלֹון · כְּסֻלֹּות · כִּסְלֹת תָּבֹור
UBS Dictionary of Biblical Hebrew © United Bible Societies, licensed CC BY-SA 4.0.
Brown-Driver-Briggs Hebrew Lexicon
[כָּסַל] vb. be or become stupid—Qal Je 10:8 ref