Rarely used in modern Japanese. Common alternatives: ない (not exist) / 亡くなる (to pass away).
dead
nonexistent; not being (there)
祖父はもう亡くなった。
My grandfather has already passed away.
父が亡かったのは十年前のことだ。
It was ten years ago that my father passed away.
祖父はまだ亡くないと皆が信じていた。
Everyone believed that our grandfather was not yet dead.