catch (one) on the flip side

slang To see one at a later time or date. Usually used as an informal farewell. Primarily heard in US. Thanks for having me over, but I'd better head out now. I'll catch you on the flip side! A: "You just missed Mary. Do you want to leave her a message?" B: "Nah, just let her know I was here and that I'll catch her on the flip side." If I don't leave right this second, I'm going to miss the train, so I'll catch y'all on the flip side!