A mingehead is a person who says or does silly, stupid or retarded things. If a person looks like a mingehead they are usually very ugly and quite scroaty/chavy. This person usually smells (has BO)and has greasy hair because they dont wash very often.
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.