When a conversation is being carried on by two people via Twitter and a third person takes over the conversation without being invited into it.
Suzy: Gracie, I can't wait for Saturday night! It's going to be an epic night.
Gracie: I know, Suzy! I'm about to wet myself with excitement!
Debra: Hey Suzy, Saturday sounds like it's going to be too much fun! Where should I meet you guys?
Suzy: Uh Gracie? Did she just twitter-jack?