A humblefloob is when someone is being very humble about something saggy, or "flooby."
Girl- Why are your balls so saggy?!
Boy- Is there something wrong with that?
Girl- What, are you saying you like that?
Boy- I don't really care.
Girl- Your being such a humblefloob!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.