used for referring to a completely different situation, often one that is difficult or that you know little about

I've parachuted and bungee jumped but rock climbing is a whole 'nother thing.

I didn't mind being called an idiot, but when it comes to attacking my family, that's a whole 'nother ballgame.

When you're dealing with children, that's a whole nother issue.

He didn't come home last night, but that’s a whole 'nother story. 他昨晚没有回家，但这完全是另一回事。

That's a topic for a whole nother post.