What does 鈍い mean?
鈍い is a Japanese adjective meaning “dull (e.g., a knife), thickheaded, slow (opposite of fast), stupid” in English. It can also be translated as “thickheaded, dull (sound, color, etc.), slow” depending on context. It is written as 鈍い in kanji, にぶい in hiragana, and nibui in romaji. This word is part of JLPT N2 vocabulary.
Example sentence
確かに彼は少々にぶいが勤勉だ。
Indeed he may be a little dull, but he is diligent.