When a guy assumes that he can 'get' a particular real life girl either to date or have sex with because he feels what he has going for him: looks, personality, status, money, job, degree, etc., are enough to impress the girl into doing so. But the problem is that girls want to 'date up', not 'date same' and definitely not 'date down', so girls that most guys think are realistically attainable to them, are not.
Girl #1: JP wants me, he keeps texting me to hang out.

Girl #2: That would be dating down girl, don't do it.

Girl #3: I think he's suffering from AGS

Girl #1 and #2: AGS?

Girl #3: Attainable Girl Syndrome!

Girl #1: Well as long as that mean he's delusional.

Girl #2: Most guys are!
by sarasplayroom.com December 3, 2009
Get the Attainable Girl Syndrome mug.