A replacement for someone's
ex-boyfriend or
ex-girlfriend who looks so much like the
ex, it's uncanny. Sometimes done deliberately to piss off the ex.
One Dude to Another: Did you see that chick with Nick?
Another: Yeah I saw her and did a double take, I thought it was his
ex, not his new chick.
One Dude: She looks so much like his
ex, she's a fuck-alike.
Another: Wait till the
ex sees the fuck-alike. She will throw a fit.