English version comes after Japanese.
海外駐在のことを「Expat」という呼び方をします。海外駐在者を意味する「Expatriate」の略ですが、国外追放とか祖国を捨てるというような意味もあるので、むやみに使わない方がいいですが、企業内での話の中ではほぼ「海外駐在」と指すと思っていていいでしょう。
I learned an English word "expat" when I joined a Germany based company. The country manager was an expat from Germany. I also learned it was an abbreviation of "expatriate" and had more meanings like "forced to move out of your country" or "to give up your nationality".