Banning a user from a web forum in such a way that the banned user is unaware of the ban. Usually takes the form of showing that user's posts/profile/etc. only to that user; other users never see them. Considered underhanded chicken-shit behavior.
Fark has turned into a bunch of shadowbanning pricks.
"I kept submitting content and got no responses, until I messaged the mods and found I was shadow banned from that forum."