While attending large events, it describes the action of someone who joins a group conversation only to stare like a lemur while remaining awkwardly silent.
Person 1: "I've had it with this onslaught of people who can't have a normal conversation. I'm saying they enter the group, say their name, and literally stare at me while the rest of us try to converse like a bug eyed lemur didn't just sit on someone's shoulder."
Person 2: "Wow, that sound like some pretty extreme lemuring."
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.