No joke
NJ is an acronym typically seen online or in text messages that means "no joke." The acronym is the opposite of JK.
NJ is used when you want to emphasize the seriousness of a comment, even though it may seem ridiculous or unbelievable. The acronym is similar to NK.
Example
NJ, he really got the senior editor position?
Baseball Slang Quiz: Can you bat 1.000?
NJ is a quick way to say "nice job" in a text or chat message. You might receive this attaboy from your friends, family, or co-workers, after you do something worth celebrating.
For example, if you make a delicious apple pie, and you share it with your friends, they might send you a message that says "NJ with that apple pie. The crust was so flaky!" They may follow up with a message asking for your pie crust recipe.