What does emotionally unavailable really mean?

So a little background information to give it context: I fell in love with X while I was dating another guy, and X and I ended up making out. Eventually I broke up with my boyfriend at the time because I realized that I was in love with X.

X had just come out of a relationship where she cheated on him and he it had obviously affected him. X and I eventually started sleeping together but he doesn't wan't a relationship beause he's "emotionally unavailable at the moment" and he doesn't want to screw up again. But he says he really likes me and enjoys hanging out with me, and he even got me a Christmas present. In his defence he is indeed always really busy at work ( having to wake up at 5 am to go to work), and one time he got drunk and he called me really upset saying that I'm really hot, clever, smart etc, and wondering why I was into someone like him. What do I do ? Do I wait for him or do I move on ( this has been going on for a year)
What does emotionally unavailable really mean?
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