To fake ignore someone in a chat room just to make a statement, then talk about said person for the next 20 minutes then, talk directly to them again giving them "another chance", then fake ignoring them again
This is a very popular term within the Yahoo chat community, and was coined in the Windows: 1 chat room. One particular member of the community would place another user on ignore, post that they had ignored them in the room publicly, then speak to them a short while later, having forgotten that they had claimed to ignore the person.
This is now a common reference within a large part of Yahoo when a user likes controversy too much to actually ignore a user which they disagree with, instead they claim to ignore the user to further controversy.
Janoring may, in some cases, be a subset, or type of trolling
I was in chat the other day talking about kittens and this girl janored me. I know she didn't really put me on ignore because she asked me my ASL five minutes later.