It's slang for calling someone rude or mean or a jerk. It's also very rude, and not something you should say around children or polite company. You would use it when you think someone is being mean on purpose, for example: "That guy tried to hit me when I said I wouldn't go on a date with him. What an asshole." "That asshole stole my wallet!" "I hope I don't sound like an asshole when I say this, but..."
@nhungmy288203 Well, it's not a very common phrase so I'm not 100% sure, but I believe "runaway bride" refers to women who start having a lot of doubts and have a higher chance of running away just before their wedding. So "runaway bride syndrome" probably refers to somebody who is likely to do that, or someone who has done that in the past
@nhungmy288203 "Hate-fucking" refers to having sex with someone you're angry at/don't like, so if I understand correctly, "you are a hate-fuck baby" means "your mom and dad hated each other when they made you" / "you were conceived by two people who hated each other." This is also a very uncommon thing to say haha