na-adjective, noun
Describes a person who is slow to understand or learn; often contrasted with 利根 (りこん, sharp-witted). Used as both a noun and a na-adjective.
Antonyms: 利根
彼は鈍根だから、一度で理解できないこともある。
He is slow-witted, so there are times he can't understand something in one go.
鈍根な人でも、努力すれば必ず成果が出る。
Even a slow-witted person can achieve results with effort.