also: にぶチン
noun
dullard; insensitive person; slow-witted person
Colloquial, mildly derogatory term for someone who is slow to understand or insensitive to others' feelings. Often used in light teasing among friends.
See also: 鈍い (にぶい)
彼はにぶちんだから、冗談が通じない。
He's a dullard, so jokes don't get through to him.
そんなにぶちんには言いたくない。
I don't want to tell such an insensitive person.
にぶい is the adjective meaning 'dull' or 'slow'; にぶちん is a colloquial noun derived from it, used to label a person.
Derived from the adjective 鈍い (にぶい, 'dull, slow') with the colloquial suffix ちん, which often adds a familiar or slightly derogatory tone to personal nouns.