1. A Concise phrase, where the context of the matter doesn't need to be explained. Usually said to someone out of the loop/ not up to date/ is not aware.
2. Having knowledge or being aware of something especially through personal experience.
You see your mate's laptop screen saver is a naked girl, but her face is covered , you know who it is, but others don't- you post it on your snapchat and put "....'s screensaver, if you know, you know"
If You Know, You Know is a word that Andrew Portugal created. He says it all the time at school and every where he goes. This funny joke is really funny now every one says it so please help and support Andrew so it does not burn out contact me at If You Know, You know :)