na-adjective, noun
Literary or formal term for ignorance and foolishness. Rare in everyday speech; more common synonyms are 愚か (おろか) or 馬鹿 (ばか).
彼の愚蒙な振る舞いに皆が呆れた。
Everyone was appalled by his foolish behavior.
愚蒙をさらけ出すような発言だった。
It was a remark that exposed his ignorance.