(This applies to some Jacobs only) Rude, inconsiderate, a backstabber, and has the filthiest mind around. No really, he won't shut up. Ever. He constantly makes fun of you and doesn't like you for who you are. He and his brainwashed drone tend to walk around the school making gross, impolite, or unfunny jokes. If you see a Jacob, make sure he's one of the good ones before you talk to him. This kind I'm describing will usually think that everything he says is hilarious and that everyone loves him. He apparently doesn't know how to apologize, and believes that he's never wrong. Oh yeah, and the bad Jacob likes to spread rumors and start drama. Be careful around Jacobs, some can be really cool people but others...
"Hey did you see that new kid, Jacob?"
"Yeah but I think he's one of the Bad Jacobs."
"Let's see, he makes fun of everyone he meets, he won't quiet himself for one second, and can't stop making filthy jokes."