Used to describe someone who's sexy, but in a wierd way. It's very rare to find someone who everyone will agree is shmexy, as it all comes down to personal taste in the end.
Guy 1: "eeew look at the state of her! She looks like Jay Leno and a pig had a kid!"
Guy 2: "hey, she isn't that bad. In fact, I think she's pretty hot.She's kinda shmexy
Guy 1: "now you mention it, she is....in a shmexy
kind of way...."