A Judgment is a document issued by the court stating the outcome of the case. If someone has a “judgment against them” then they lost the case, and in debt collection cases, they now owe the plaintiff money.
Pro Tip: Judgment can be spelled either "Judgement" or "Judgment" — without an "e". If you want to look like you know what you're doing in the US, spell it without an "e": "Judgment". The spelling with an "e" is preferred in the UK. America fought a revolution for a reason.