na-adjective
Rare literary term for a person who is slow-witted or lacking in intelligence. Not used in everyday conversation; more common synonyms include 愚か (おろか) or 鈍い (にぶい).
彼は自らを駑鈍と称したが、実際は鋭い洞察力を持っていた。
He called himself dull-witted, but in fact he had sharp insight.