Is this slander or just gossip?

Here's the problem with slander: Not only do you have to prove that the information this former co-worker is spouting is false, and that he/she knows it's false, you also have to prove that this person is lying about you with malicious intent. If you were to take this person to court, he/she could always say that the things he/she was saying were "rumor mill" and that he/she was not deliberately trying to defame your character. Makes it very difficult to meet that legal burden of knowingly making false statements with deliberate intent of malice...