Lacking common sense; unreasonable or thoughtless behavior that goes against general social norms.
そんな非常識な発言は場の空気を壊すよ。
That kind of thoughtless remark will ruin the atmosphere.
遅刻しても謝らないのは非常識だと思う。
I think it's inconsiderate not to apologize when you're late.
彼の要求は非常識だと全員が感じた。
Everyone felt his demand was unreasonable.