Is there any slang word that describes somebody who doesn't show up when you date him?
The most common slang term I've heard for this is stood up. In 5 stages of dealing with being stood up (CNN), the opening lines are:
Nobody likes to get stood up! But it does happen. And if you date long enough, it's bound to happen. It's so embarrassing. You get left at a restaurant, the dude never shows, the man of your dreams just doesn't call.
I belive that the correct term here would be
Someone who does not show up when they had previously stated they will. Also, someone who has no intention of showing up, but acts like they will or want to show up only to mess with your feelings.
Tim is such a flaker. I can't believe that he bailed out the very last minute! I'm definitely not inviting him to hang out next time.
to ignore someone or something; to skip an appointment with someone; to not attend something where one is expected. He decided to sleep in and blow this class off. It wasn't right for you to just blow off an old friend the way you did.