Unable to judge and improvise interactions with other people in a acceptable or 'normal' manner. By a mix of being too keen or plain ignorant the socially inept seem to live in their own world exempt from who they're talking to.
Josie : *Winks flirtingly*
Ben : Oh do you have something in your eye? Want me to go get you some eye drops?
Josie : You are so socially inept *walks off*