IPA: /ˈwɪt.ləs/
KK: /ˈwɪtləs/
Not having intelligence or good sense; foolish or silly.
His witless remarks made everyone in the room uncomfortable.
Comparative: more witless
Superlative: most witless
Witless → It is formed from "wit" (from Old English "wita", meaning knowledge or understanding) and "-less" (meaning without). The word "witless" means lacking knowledge or understanding, or being without wit.
Think of someone who is 'without' ('-less') 'knowledge' ('wit') — that's why witless means lacking in understanding.