A formal, somewhat literary term for a lack of intelligence or knowledge. Often used in written or critical contexts.
彼の愚昧な発言に皆が呆れた。
Everyone was astonished by his foolish remarks.
その政策は国民を愚昧と見なしている。
That policy treats the people as ignorant.
A Sino-Japanese compound of 愚 (foolish) and 昧 (dark, ignorant). The exact historical derivation is uncertain, but the combination has been used in classical Chinese and later adopted into formal Japanese.