Regrettable or vexing; expressing disappointment or that something is unfortunate.
彼が辞めるとは心外だ。
I'm surprised and disappointed that he's quitting.
その扱いは心外に思う。
I find that treatment upsetting.
そんなことを言われるとは心外だよ。
I'm really surprised and hurt to be told something like that.
Unthinkable or wholly unexpected; expresses strong surprise at something unforeseen.
彼がそんなミスをするとは心外だ。
It's completely unexpected that he would make such a mistake.
あの親切な人が裏切るとは心外だった。
I was astonished that such a kind person would betray us.