What do guys mean by "hang out"?

This has happened to me twice, with two different guys. I get to be friends with a guy, and then he asks me to hang out. Thinking he means as friends, I say sure. Then when we're hanging out, he acts like we're on a date. The first time it happened I just thought it was something with that guy (especially because he ended up being really weird). Then it happened a second time with another guy who wasn't as weird. Was I wrong to think "hang out" actually meant "hang out"? I am the kind of person that misses social cues sometimes, so its very possible that's what happened.