disapproval If you say that someone is a dunce, you think they are rather stupid because they find it difficult or impossible to learn what someone is trying to teach them. Michael may have been a dunce at mathematics, but he was gifted at languages. someone who is slow at learning things (John Duns Scotus (1266?-1308), Scottish religious thinker)
Furnishing little delight, spirit, or variety; uninteresting; tedious; cheerless; gloomy; melancholy; depressing; as, a dull story or sermon; a dull occupation or period; hence, cloudy; overcast; as, a dull day
these words are used to express a low opinion of someone's intelligence Insensible; unfeeling
Not bright or clear to the eye; wanting in liveliness of color or luster; not vivid; obscure; dim; as, a dull fire or lamp; a dull red or yellow; a dull mirror