What does 災難 (さいなん, sainan) mean?

今日(きょう)は本当(ほんとう)に災難(さいなん)な一日(いちにち)だった。

Today was truly a disastrous day.

事故(じこ)に遭(あ)うなんて、とんだ災難(さいなん)でしたね。

Having an accident like that was quite a disaster, wasn't it.