A colloquial conditional phrase meaning 'if that's the case' or 'in that case', used to respond to someone's remark or a given situation.
明日休みだったら、映画に行こう。
If you're off tomorrow, let's go to a movie.
それが本当だったら、早く知らせてください。
If that's true, please let me know quickly.
行けないんだったら、代わりの人を探すね。
If you can't go, I'll look for someone to go instead.