na-adjective, noun
insensitive; inconsiderate; callous; thick-skinned
Describes a person or behavior that lacks consideration for others' feelings, often blunt or tactless. Can be used as a noun or adjectival noun.
彼は無神経な発言で周りを困らせた。
He upset those around him with his insensitive remarks.
そんなことを言うなんて、無神経すぎるよ。
Saying something like that is just too thoughtless.