A person or group of people who, despite acting cooperative and supportive to your face, attempt to negatively influence others' opinions of you, cause financial or emotional harm to you or generally throw shade in the direction of you, your family or your business.
Regina is a total shademister.
Regina: Oh my God, I love your skirt! Where did you get it?
Lea Edwards: It was my mom's in the '80s.
Regina: Vintage, so adorable.
Lea Edwards: Thanks.
Regina: after girl walks away That is the ugliest effing skirt I've ever seen.
Riot Hospitality Group is a bunch of shademisters for opening their clubs during the Evening Entertainment Groups's Holiday Party.
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.