HelloGoodbye Friend
Friends you never talk to albeit saying "Hello" and "Goodbye" while passing in the halls. These friends are usually people that you have classes with, people you've done a group project with, lab partners, etc.
"Sara is your friend right?"
"Nah, we did a project together last year; she's a HelloGoodbye Friend."
"Nah, we did a project together last year; she's a HelloGoodbye Friend."