Also found in: Acronyms.
An initialism of "just so you know," used primarily in text messages and online communications to inform someone of something. A: "I'm probably going to be about 30–40 minutes late, JSYK." B: "OK, no problem." That picture you posted was from, like, five years ago JSYK. Not really relevant anymore.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.