A person or persons who mumble incessantly to spite the people around them. The people in question mumble continuously in order to fill a space or situation with as much interference as humanly possible with the aim of getting under the skin of others in their vicinity. These types are often referred to as being from "MUMBOLIA". Also they repeat the same mumble sound often which would be referred to as a "MUMBOLIANISM". These people are found quite readily in the realms of the HAM radio operator and are the bane of "normal speaking radio stations on the air".
"Oh God sounds like the Mumbolians are out in forcetoday!"
"CQ CQ any stations outside Mumbolia on this frequency!"
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.