Are you otherwise engaged with these people? Or, is it a bit more detached, like you happen to be on the same bus or cafeteria? If you are by yourself and have

Are you otherwise engaged with these people? Or, is it a bit more detached, like you happen to be on the same bus or cafeteria? If you are by yourself and have something to signal that you aren't available for casual conversation (a book, headphones, your phone, etc) I don't think that counts. I think people are firing off at you is because the context is a situation where some one rightfully would expect your attention, like talking to a friend or any other sort of scheduled activity.