Refers to a lack of intelligence or talent, either as an abstract quality or as a person who is slow-witted. Often used in self-deprecating or critical contexts.
鈍才 means a person of dull or mediocre talent, the opposite of the bright, gifted 秀才.
Etymology
Composed of 鈍 (dull, slow) and 才 (talent, ability). The exact historical derivation is uncertain, but the combination directly conveys the meaning of dull talent or a dull person.