"JK" has casual usages regarding chit-chat, texting, or posting on social media. An informative example would be: "I just won the lottery! JK." This would indicate that the statement was pure joke material. This helps signify to a receptor that some statement is not intended to be taken seriously. Oftentimes, do you know jk meaning "JK" serves as a modifier to tease someone in a somewhat lighter or innocent way, thus softening a mocking comment or a sarcastic remark?