When your girlfriend's, or a friend who's a girl, or a female who walks by you, smells like someone opened a can of tuna coming from the vaginal area. It normally means she is in desperate need for a douche. Or a shower. And use lots of soap. Because that stench is hard to get rid of.
Two guys walk past a girl in Wal-Mart
Guy 1: DUDE! Did you smell that?!
Guy 2: Yeah bro. That was definitely a Flounder Bounder.
Guy 1: Hopefully she's making her way to the douching isle.